sleep
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n.
- A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli. During sleep the brain in humans and other mammals undergoes a characteristic cycle of brain-wave activity that includes intervals of dreaming.
- A period of this form of rest.
- A state of inactivity resembling or suggesting sleep; unconsciousness, dormancy, hibernation, or death.
- Botany. The folding together of leaflets or petals at night or in the absence of light.
- A crust of dried tears or mucus normally forming around the inner rim of the eye during sleep.
v., slept (slĕpt), sleep·ing, sleeps. v.intr.
- To be in the state of sleep or to fall asleep.
- To be in a condition resembling sleep.
- To pass or get rid of by sleeping: slept away the day; went home to sleep off the headache.
- To provide sleeping accommodations for: This tent sleeps three comfortably.
sleep around Informal.
- To be sexually active with more than one partner.
- To sleep at one's place of employment: a butler and a chauffeur who sleep in.
- To oversleep: I missed the morning train because I slept in.
- To sleep late on purpose: After this week's work, I will sleep in on Saturday.
- To think about (something) overnight before deciding.
- To sleep at one's own home, not at one's place of employment.
- To sleep away from one's home.
- To spend the night as a guest in another's home.
- To have sexual relations.
- To have sexual relations with.
sleep like a log (or rock)
- To sleep very deeply.
[Middle English slepe, from Old English slæp.]
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Natural periodic suspension of consciousness during which the powers of the body are restored. Humans normally sleep at night, whereas nocturnal species sleep during the day. Adult humans sleep between six and nine hours per night, though increasing numbers of people sleep less than six hours. Sleep is divided into two main types: REM (rapid-eye-movement) and NREM (non-REM), each of which recurs cyclically several times during a normal period of sleep. REM sleep is characterized by increased neuronal activity of the forebrain and midbrain, by depressed muscle tone, and by dreaming ( dream), rapid eye movements, and vascular congestion of the sex organs. NREM sleep is divided into stages, the last of which is the deep, restorative, quiet sleep commonly associated with a good night's rest. insomnia; narcolepsy.
For more information on sleep, visit Britannica.com.
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We spend about one-third of our lives sleeping, but exactly why we need sleep is the subject of much dispute. Traditional views emphasize sleep's restorative value; another view emphasizes the advantages of a period of immobility, for example, in conserving energy. Lack of sleep is associated with lower reaction times, reduced muscular coordination, and poor vigilance. It can also produce distinct alterations in personality.
Although the average person sleeps between 7-8 hours a night, there is no single standard number of hours of sleep that can be applied to everyone. Each person has to determine his or her own optimum. Exercise often restores normal sleep patterns to people who suffer sleeping disorders, and those who exercise vigorously generally need more sleep than sedentary people. See also insomnia.
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Sleep is a complex behaviour that is an integral part of the body's strategic adaptation to daily changes in light and temperature. Because we lose consciousness so dramatically when we fall asleep, it was erroneously assumed that brain activity ceased in sleep. The presence of vivid dreams made such a simplistic theory unlikely and, during the past fifty years, scientific research on the brain and body has shown sleep to be richly variegated, exquisitely controlled, and essential to life. It is now also clear that sleep is not always benign but has its own built-in propensity for disorder and disease.
The rich variegation of sleep phenomena can already be appreciated in its definition as a behaviour characterized by postural immobility (but with periodic changes in body position and muscle tone), by decreased response to external stimuli (but with marked fluctuations in threshold to response), by selective sensitivity to some stimuli, and by an orderly sequence of electrical and chemical changes in the brain that affect the entire body and greatly alter the mind. Clearly, sleep is an active, global, organismic state requiring central control by the brain and affording the brain and body a wide variety of functional opportunities.
Subjective experience was not the only obstacle to appreciation of the manifold complexity of sleep. Because of our modesty, we do not normally welcome the observation of our sleep. And because we all tend to sleep at the same time, there is no one to watch over those few who are willing to be observed. The development of sleep laboratories in the last half century has begun to counter these trends and to create the detailed picture we have today, but naturalistic studies of sleep are still woefully inadequate.
Sleep laboratory studies
Most sleep laboratories consist of two rooms; one with a bed for the subject, connected via a one-way window and by cables to the other, an instrument room where a technician monitors the sleeping subject (sometimes also by video). Recordings are made of electrical signs from the brain (electroencephalogram or EEG) ; from the eye (electro-oculogram or EOG) ; and from the muscles (electromyogram or EMG). A polygraph is used to keep track (graph) of the several (poly) signals simultaneously. Other important bodily functions, like body temperature, breathing, heart rate, blood pressure, and even sex organ volume, can also be recorded.
A typical night of sleep in an adult human is divided into four or five distinct cycles of body and brain activity. Each cycle begins with a relaxation phase, showing declines in brain wave (EEG) activation, muscle tone (EMG), eye movement (EOG), heart rate, breathing rate, and blood pressure, all of which typically reach a nadir after 45-60 minutes. This relaxation phase then gradually gives way to an activation phase, in which many of the brain and bodily functions resume the high levels of the awake state. In the face of this activation, sleep is maintained by the active suppression of sensory (input) signals and motor (output) commands.
Over the course of the night the length and depth of the relaxation phase (which is called quiet, NREM (non-rapid eye movement), or EEG slow-wave sleep) declines as the duration and intensity of the activation phase (called active, REM or EEG fast-wave sleep) increases. About 70-80% of an average sleep bout of 6.5-8.0 hours consists of NREM sleep, while 20-30% is REM. Other bodily functions which are associated with NREM sleep include the secretion of the hormones regulating growth and sexual maturation. REM sleep is associated with profound muscle relaxation and with sex organ distension, including full erection (and is therefore a built-in test of physiological potency), and a loss of the capacity for internal temperature regulation. The rapid eye movements that give REM sleep its name are not continuous but occur in flurries or clusters, each of which is associated with (sometimes dramatic) increases in the rate, or with irregularity, of heartbeat and breathing. Awakenings which follow these REM clusters are very likely to yield long and detailed reports of dreaming.
Variations in sleep
Sleep varies markedly over the life cycle as well as overnight. New-born infants lack the capacity for long, deep NREM sleep. This only develops, with brain maturation, during childhood and adolescence. But babies have an exaggerated propensity for REM sleep, often entering it directly from waking (so it can easily be observed by curious carers). Since sleep duration is about twice as long in neonates (16 vs. 8 hours) and REM is twice as common (50% vs. 25%), the new-born spends four times longer in REM than does the adult (8 vs. 2 hours). REM sleep declines dramatically as sleep depth increases with brain maturation and the emergence of the adult pattern.
But this is not the end of the dynamism of sleep development. The capacity for deep NREM sleep falls precipitately between ages 30 and 40. This leads to a normal decline in the ability to sustain sleep and to feel deeply rested by it. REM sleep remains relatively stable, but its decline may cause further deterioration of sleep quality after age 60, especially as other medical problems interfere with sleep.
Individuals also show marked differences in sleep behaviour. Most of us lie between two extreme ends of a bell-shaped curve of sleep length and efficiency. At one end are the short-sleepers, who need as few as 3-5 hours, and at the other are long-sleepers, who need 8-11 hours to feel rested and refreshed by sleep. Short-sleepers tend to be energetic, active, and productive, while long-sleepers tend to be lethargic, sedentary, and reflective. Society, with its interest in tight schedules and productivity, is kind to short but merciless to long-sleepers. Long-sleepers are ill-advised to seek professions, like medicine, which greatly curtail sleep.
Even within individuals of a given sleep need and age, sleep varies from night to night, and poor or lost sleep tends to be rapidly compensated. This reciprocal dynamic is dramatically revealed by studies in which one or another sleep phase or time is deliberately altered and the recovery process is monitored.
Much has been learned about sleep from laboratory studies of non-human animals. For example, the diversity of sleep behaviour increases as the brain becomes more and more specialized during evolution. Below the level of the reptiles (who have clear-cut NREM sleep but not REM), it is difficult to distinguish sleep from simple inactivity. REM sleep first appears in birds and then only fleetingly, because while hatchlings have it in abundance, adults have little or none. REM sleep is first clearly and enduringly seen in mammals, suggesting a relationship to the two features which distinguish that class of animal: large, highly developed brains and the capacity for strong internal temperature control.
Brain mechanisms of sleep
There is exquisite control of sleep by the brain. In mammals, sleep is one of the key bodily functions controlled by the body clock in the hypothalamus. By these means it is also tied to the rhythm of body temperature, such that sleep occurs as body temperature falls and waking occurs when body temperature is highest. For most animals, including humans, these peaks in alertness and energy availability occur during the daylight hours, but animals (like rats) that rely more on smell than on vision are active at night and sleep in the daytime. In very hot climates humans may also shift their activity into the darker, cooler night and have a siesta during the forbiddingly hot period of the early afternoon.
The body clock times the occurrence of sleep via its direct nervous connection between the hypothalamus and other subcortical structures in the lower brain. Of particular importance are those collections of brain cells in the brain stem which manufacture and liberate from their endings two brain chemicals, noradrenaline (norepinephrine) and serotonin, which appear to have energizing effects needed for the waking functions of the brain and the body. In order for sleep to occur the activity of these brain cells must be quelled by the mechanism of inhibition. As their activity is more and more completely diminished, another group of cells becomes increasingly active and liberates more and more molecules of another chemical (acetylcholine), which appears to mediate restorative functions throughout the body and the brain. It is the reciprocal interaction of the two cell groups that appears to provide the basis of the cyclic alternation of NREM and REM sleep and their functional differentiation.
Functions of sleep
Sleep is vitally necessary. Recent experiments on the effects of prolonged sleep deprivation give hints as to why even short-term sleep loss is so disabling and why it is so vigorously compensated by the brain. If sleep deprivation is extended beyond two weeks, rats develop a distinctive group of signs that inevitably leads to their demise. Their skin breaks down and they show an increasing craving for food but cannot maintain their body weight no matter how much they eat. At the same time they develop more and more determined heat-seeking behaviour, as they cannot control their body temperatures when exposed to normal variation in environmental temperature. Short of these extreme effects, more modest sleep deprivation has been shown to create a wide variety of difficulties. Taken together these suggest that sleep may normally play an important role in the maintenance of such important bodily functions as the immune response and metabolic balance, as well as such critical mental functions as attentiveness, learning and memory, and emotional equilibrium. Shakespeare may have been correct when he said that sleep ‘knits up the raveled sleeve of care’, but he was underestimating the more active developmental and survival functions of sleep.
— J. Allan Hobson
See also dreaming; electroencephalogram; sleep disorders; snoring.
Roget's Thesaurus:
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sleep
also sleep with
noun
- The natural recurring condition of suspended consciousness by which the body rests: slumber. Slang shuteye. Idioms: land of Nod, the arms of Morpheus. See awareness/unawareness.
verb
- To be asleep: slumber. Idioms: be in the land of Nod, catch some shuteye, sleep like alogrocktop, sleep tight. See awareness/unawareness.
phrasal verb - sleep in
- To sleep longer than intended: oversleep. See awareness/unawareness.
phrasal verb - sleep with
- To engage in sexual relations with: bed, copulate, couple, have, mate, take. Idioms: go to bed with, make love, make whoopee, roll in the hay. See sex/asexual.
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Idioms beginning with sleep:
sleep around
sleep a wink, not
sleep like a log
sleep on something
sleep over
sleep with
See also let sleeping dogs lie; lose sleep over; put to sleep. Also see under asleep.
Antonyms by Answers.com:
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sleep
n
Definition: suspension of consciousness
Antonyms: awakeness, awakening, consciousness, wakefulness
v
Definition: suspend consciousness
Antonyms: awaken, wake, waken
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1. [techspeak] To relinquish a claim (of a process on a multitasking system) for service; to indicate to the scheduler that a process may be deactivated until some given event occurs or a specified time delay elapses.
2. In jargon, used very similarly to v. block; also in sleep on, syn.: with block on. Often used to indicate that the speaker has relinquished a demand for resources until some (possibly unspecified) external event: “They can't get the fix I've been asking for into the next release, so I'm going to sleep on it until the release, then start hassling them again.”
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Definition
Sleep is a biological imperative critical to the maintenance of mental and physical health. It is a state of lessened consciousness and decreased physical activity during which the organism slows down and repairs itself. The sleep cycle involves two distinct phases that alternate cyclically from light sleep to deep then deeper and deepest sleep throughout the sleep period. There are two main phases of sleep.
- rapid eye movement (REM) sleep, during which dreaming occurs
- non-rapid eye movement (NREM) or slow-wave sleep (SWS)
Description
The timing and progression of the sleep cycle and the total amount of nightly sleep required for optimal health varies from infancy to adulthood, depending on developmental stage and temperament. Children, particularly infants, require the most sleep during a 24-hour period. The natural sleep-wake cycle, governed by an internal "biological clock," tends toward a 25-hour day. It is affected by the relative balance of light and darkness in the environment. As darkness approaches, the hormone melatonin is secreted by the pineal gland and signals the brain that it is time to sleep.
Nrem Deep Sleep
Sleep begins in stage one of the sleep phase known as NREM, or non-rapid eye movement, sleep. NREM sleep has four stages: light sleep, deeper sleep, and two stages of deepest sleep. Stage one is the "drifting off" period of light sleep in the transition between wakefulness and sleep and comprises about 5 percent of the entire sleep period. Stage two sleep involves a change in brain-wave patterns and increased resistance to arousal and accounts for 45–55 percent of total sleep time. Stages three and four are the deepest levels of sleep and occur only in the first third of the sleep period. NREM stage four sleep usually takes up 12 to 15 percent of total sleep time. Sleep terrors, sleep walking, and bedwetting episodes generally occur within stage four sleep or during partial arousals from this sleep stage.
It typically takes about 90 minutes to cycle through the four deepening stages of NREM sleep before onset of the second phase of sleep known as REM or dream sleep.
Rem Dream Sleep
Rapid eye movement (REM) sleep is qualitatively different from NREM sleep. REM sleep is characterized by extensive central nervous system (CNS) activity with an increase in brain metabolism accompanied by the vivid imagery of dreams. During REM sleep the body is nearly paralyzed, a condition called "atonic," that serves to inhibit the dreamer from physical movement during active dreaming.
"Waking and dreaming are two states of consciousness, with differences that depend on chemistry," according to J. Allan Hobson, professor of psychiatry at Harvard Medical School. Physical activity and thought are suppressed in sleep, but the brain nonetheless remains active "processing information, consolidating and revising memory, and learning newly acquired skills." The brain self-activates, radically changing its chemical climate from wakefulness to sleep states.
REM sleep is also known as "paradoxical sleep" because muscle activity is suppressed even as the CNS registers intense brain activity and spontaneous rapid eye movements can be observed. Brain-wave monitoring of REM sleep with an electroencephalograph (EEG) reveals a low-voltage, fast-frequency, non-alpha wave record. Beyond infancy, REM sleep comprises 20–25 percent of the entire sleep period. This sleep phase is concerned with memory and the consolidation of new information.
Infancy
Newborn infants usually sleep for brief periods at a time around the clock, with the total of day and nighttime sleep roughly equal. A newborn's total sleep need is from 16 to 18 hours in every 24-hour period. Newborns spend approximately 50 percent of their sleep period in the REM phase. Infants are most easily awakened during this phase of sleep that is accompanied by yawning, squirming, and quiet vocalizations.
Infants move through REM and non-REM sleep stages in a 90 minute cycle, and they rise to a near-waking state every three to four hours, more often in breastfed infants. By about six months of age, babies usually will sleep through the night for 12 or more hours and will continue to nap several times throughout the day.
Researchers conducting a 2004 survey for the National Sleep Foundation discovered that children in every age group fail to meet even the low-end requirements for adequate sleep. By the third month of life, a child's sleep requirement is about 14 to 15 out of every 24 hours, a need that continues until about 11 months of age. However, research indicates that children age three months to 11 months sleep only 12.7 hours on average.
Toddlerhood
Toddlers are far more physically active than infants, and their sleeping behavior and the timing of sleep cycles reflects their maturing brains. A toddler will spend only about 30 percent of her sleep time in REM dream sleep. Toddlers on average require 12 to 14 hours of sleep and may no longer need an afternoon nap to meet this sleep requirement. But research shows that children in the one to three-year-old range may actually average only about 11.7 hours of sleep.
Preschool
Children in this age group tend to be more troubled with nightmares and night terrors than younger children. They may resist going to bed at night because of fear of the dark or of some monster lurking under the bed. Parental reassurance and comfort and the addition of a night light may alleviate some of these concerns. Preschool children may also feel anxiety around the issue of toilet training and bedwetting.
School Age
School-age children require from eight to 10 hours of sleep nightly. Adequate sleep is especially important as school children's lives become busier and stress levels rise. Sleep disruptions such as nightmares tend to increase with this age group as the child has more life experiences and anxieties to process. Parents should also monitor the child's use of caffeinated beverages which can cause sleep difficulties and add to the overall loss of adequate sleep.
Adolescents require at least 10 hours of nightly sleep. This is a busy time when many teens' lifestyles include school, work, sports, and other extracurricular activities, as well as socializing with peers. This increase in activity, together with early-morning school schedules, leaves little time for adequate sleep. Various psychological disorders also may trouble the adolescent, particularly anxiety and depression. Parents should pay attention to a young teen who shows sudden changes in eating habits, loss of interest in usual activities, and other behavioral clues that may indicate onset of depression.
Common Problems
According to the "2004 Sleep in America Poll" published by the National Sleep Foundation, 69 percent of children younger than age 10 experience problems with sleep that may occur as often as several times a week. Sleep disruptions in children are usually a normal symptom of central nervous system development. In older children sleep disruptions may increase and intensify due to external stressors in the home or school environment. Sleep difficulties can also be a sign of physical or mental health problems. They are often present in children with attention-deficit/hyperactivity disorder (AD/HD) and in children who have experienced physical, psychological, or sexual abuse.
Childhood sleep problems and parasomnias include:
- Bedwetting: A common sleep problem characterized by involuntary urination during sleep. This is a routine occurrence in children up to five years of age. Bedwetting is also called "nocturnal enuresis."
- Nightmares: A common parasomnia characterized by dreams with frightening psychological content, a feeling of imminent physical danger, and a sensation of being trapped or suffocated. Nightmares occur during REM, or dream-time, sleep and trigger a partial or full awakening. The word "mare" in Old English means "demon."
- Insomnia: Difficulty falling asleep and remaining asleep, or early-morning awakenings. Insomnia may be short-term, due to stress or physical or psychological problems, or may be due to the lack of a healthy bedtime routine.
- Night terrors: A common childhood sleep disruption characterized by an abrupt arousal from stage 4 sleep within the first hour of the sleep period. The child may sit bolt upright in acute terror, screaming inconsolably. Night terrors are a confusional arousal resulting from immature sleep patterns with an intense activation of the flight or fight emotion. They occur in the deepest stage of slow-wave non-REM sleep. Night terrors are also called "pavor nocturnus."
- Sleep apnea: A serious and potentially life-threatening sleep disruption characterized by brief interruptions of airflow during sleep and frequent partial arousals throughout the night. Sleep apnea is less common than other sleep disturbances, occurring in about 2 percent of children.
- Sleep bruxism: A sleep disturbance characterized by grinding the teeth or clenching of the jaws during sleep. Sleep bruxism is common among children of all ages. This sleep problem usually subsides over time.
- Sleep rocking and head banging: A sleep disturbance characterized by rhythmical movements of the body during sleep. Rhythmical movements may be observed in children as young as six months. More dramatic movements, involving head banging and rocking, occur in as many as 60 percent of nine-month-old children. These sleep disturbances tend to decrease with age, appearing in only about 5 percent of children over two years of age.
- Sleep walking: A sleep disturbance characterized by a partial-arousal involving walking about for a few steps, or for much longer distances, with a glassy, trance-like appearance to the eyes. Sleepwalking occurs in the deepest stages of slow-wave, non-REM sleep within the first few hours of sleep onset. Researchers have found that as many as 15–30 percent of children experience at least one sleepwalking episode. Sleepwalking can be triggered by external stimuli, such as an abrupt noise, or by moving a sleeping child to a standing position. This sleep disturbance tends to run in families. Sleepwalking is also called "somnambulism."
Losing Sleep
All children need regular and adequate sleep to assure optimal mental and physical health. Sleeping patterns developed in infancy usually persist into adulthood. It is important that parents help the child to establish a healthy bedtime routine that will assure adequate sleep time, minimize bedtime struggles, and help to reduce the occurrence of common childhood sleep problems.
As reported by Steven Reinberg, research by Maria M. Wong of the University of Michigan, published in 2004 in the journal Alcoholism: Clinical and Experimental Research, cautions parents to pay more attention to their children's sleep habits. "Sleep problems are a risk factor for alcohol and drug problems," Wong concluded from data obtained in the first study to link alcohol and drug use with sleep disorders in early childhood. The study obtained sleep data from 257 boys ages three to five years and followed them until they were 12–14 years old. Almost half of the children in the study who experienced childhood sleep problems began using alcohol and drugs by the time they were 14 years old.
In many households, electronic distractions interfere with the establishment of a regular bedtime routine that would help a child to settle down and prepare for restful sleep. Calming-down activities, such as being read to by a parent, have been replaced with electronic stimulation resulting in less sleep time.
As reported in Manchester Online, Luci Wiggs, a research fellow at Oxford University, is co-author of a 2004 poll of more than 1,000 parents with children four to 10 years of age. She found that 67 percent of these children had a television, computer, or game machine in their bedroom. These stimulating diversions, which she calls "digital distractions," resulted in a cumulative sleep deficit for at least one fifth of the children surveyed that may "compromise children's physical health, academic achievements, and mental health."
Children who consume caffeine throughout the day, in soda or iced tea beverages, also lose the sleep required for optimal health and cognitive functioning. A survey by the National Sleep Foundation released in 2004 found that 26 percent of children ages three and older drink at least one caffeinated beverage a day and suffer a loss of about 3.5 hours of sleep each week.
Parental Concerns
Parents are on a journey of discovery with each child whose temperament, biology, and sleep habits result in a unique sleep-wake pattern. It can be frustrating when children's sleep habits do not conform to the household schedule. Helping the child develop good sleep habits in childhood takes time and parental attention, but it will have beneficial results throughout life. An understanding of the changing patterns of the typical sleep-wake cycle in children will help alleviate any unfounded concerns. Maintaining a sleep diary for each child will provide the parent with baseline information in assessing the nature and severity of childhood sleep problems. Observant parents will come to recognize unusual sleep disruptions or those that persist or intensify.
When to Call the Doctor
Developmental changes throughout childhood bring differences in the sleep-wake cycle and in the type and frequency of parasomnias that may interrupt sleep. Medical consultation to rule out illness, infection, or injury is prudent if the child's sleep problems prevent adequate sleep and result in an ongoing sleep deficit. As reported by News-Medical in Child Health News, children's sleep problems should be taken seriously as they may be a "'marker' for predicting later risk of early adolescent substance use." In the same article, University of Michigan psychiatry professor Kirk Brower, who has studied "the interplay of alcohol and sleep in adults," stressed that "The finding does not mean there's a cause-and-effect relationship."
Consultation with a child psychologist may be helpful if frightening dreams intensify and become more frequent as this may indicate a particular problem or life circumstance that needs to be changed or one that the child may need extra help working through.
Most childhood sleep disturbances will diminish over time as the brain matures and a regular sleep-wake cycle is established. Parental guidance is crucial to development of healthy sleep habits in children.
Resources
Books
Hobson, J. Allan. Dreaming: An Introduction to the Science of Sleep. Oxford: Oxford University Press, 2002.
Moorcroft, William H. Understanding Sleep and Dreaming. New York: Kluwer Academic/Plenum Publishers, 2003.
Schroeder, Carolyn S., and Betty N. Gordon. Assessment and Treatment of Childhood Problems, 2nd ed. New York: Guildford Press, 2002.
Periodicals
"Kids' Sleep Problems Can Portend Alcohol and Drug Use." Connecticut Post, April 15, 2004. Available online at www.lexis-nexis.com (accessed October 6, 2004).
Moss, Lyndsay. "Computers and Games 'Keeping Children Awake."' Press Association News, March 26, 2004. Available online at
Wilmott, Bob. "Many Children Fall Short of the Sleep They Need." St. Louis Post-Dispatch, April 26, 2004. Available online at www.lexis-nexis.com (accessed August 3, 2004).
Organizations
American Sleep Disorders Association. 1610 14th Street, NW, Suite 300, Rochester, MN 55901–2201. Web site: www.sleepnet.com/asda.htm.
National Sleep Foundation. 1522 K Street, NW, Suite 500, Washington, DC, 20005. Web site: www.livingwithillness.com/id174.htm.
Web Sites
"Children kept awake by computers and games." Manchester Online, March 26, 2004. Available online at wwwmanchesteronline.co.uk/business/technology/s/85/85453_children_kept_awake_by_computers_and_games.html (accessed October 7, 2004).
"Children's Bedtime Routines: Sound Sleeping Advice." Mayo Foundation for Medical Education and Research, September 23, 2003. Available online at www.mayoclinic.com/invoke.cfm?id=CC00020. (accessed July 23, 2004).
"Computers 'rob children of sleep."' BBC News. Available online at
Driver, Helen. "Parasomnias." Canadian Sleep Society. Available online at www.css.to/sleep/disorders/parasomnia.htm (accessed July 29, 2004).
Reinberg, Steven. "Kids' Sleep Problems Can Portend Alcohol and Drug Use." Healthfinder News. Available online at www.healthfinder.gov/news/newsstory.asp?docID=518390 (accessed October 7, 2004).
"Sleep Behavior Problems (Parasomnias)." Kids Health for Parents. Available online at www.kidshealth.org/parent/general/sleep/parasomnia.html (accessed July 26, 2004).
"Sound sleep in infants lessens likelihood of drug abuse in later years." News-Medical in Child Health News, April 16, 2004. Available online at www.news-medical.net/print_article.asp?id=545 (accessed October 7, 2004).
"Tips for Healthy Sleep." American Sleep Disorders Association. Available online at www.slepnet.com/ (accessed August 4, 2004).
[Article by: Clare Hanrahan]
A physiological condition of relative immobility and natural unconsciousness when there is an increased reluctance to respond to stimulation and when many bodily functions are maintained at a minimal level of activity. There is much controversy concerning the significance of sleep. Traditional views emphasize its restorative value; another view emphasizes the advantages of the associated immobility (for example, in conserving energy expenditure). See also REM sleep, sleep deprivation.
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sleep
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From our Archives: Today's Highlights, April 21, 2005
Columbia Encyclopedia:
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sleep
sleep, resting state in which an individual becomes relatively quiescent and relatively unaware of the environment. During sleep, which is in part a period of rest and relaxation, most physiological functions such as body temperature, blood pressure, and rate of breathing and heartbeat decrease. However, sleep is also a time of repair and growth, and some tissues, e.g., epithelium, proliferate more rapidly during sleep.
In humans, sleep occurs in cyclical patterns; in each cycle of 11/2 to 2 hr, the sleeper moves through four stages of sleep, from Stage 1 to Stage 4, and back again to Stage 1. In the first stage, low-frequency, low-amplitude theta waves characterize brain activity. The stage usually lasts only several minutes, before the individual drifts into Stage 2 sleep, and the brain moves into low-frequency, high-amplitude waves. Stage 3 signals an increase of low-frequency, high-amplitude delta waves, and at Stage 4 sleep these delta waves account for more than half of all brain wave activity (see electroencephalography). Rapid-eye-movement (REM) sleep occurs during Stage 1 sleep at the end of each cycle, and people woken up at this time usually report that they have been dreaming. Dream deprivation or sleep deprivation results in detrimental changes in personality, perceptual processes, and intellectual functioning. There is some evidence that emotional and environmental deprivation disrupts the sleep patterns of young children, which in turn inhibits the secretion of growth hormone, normally secreted maximally during sleep.
The amount of sleep needed depends on both the individual and the environment: For instance, worrying, critical individuals tend to need both more sleep and more dream sleep than easygoing ones, and stress and worry during the day result in an increase in REM sleep. It has been hypothesized that while deeper stages of sleep are physically restorative, REM sleep is psychically restorative. REM sleep is also believed to integrate new information in the brain and to reactivate the sleeping brain without waking the sleeper. There is evidence that the hypothalamus and thalamus of the brain initiate sleep and that part of the midbrain acts as an arousal system. See also dream; insomnia; narcolepsy; sleep apnea.
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A third of our lives is spent in sleep. Of the remainder, some is spent in wishing that our small children would sleep longer, and, during our later years, some is spent wishing that our sleep was less broken. What is sleep? It is a healthy state of inertia and unresponsiveness that is recurrently imposed by unknown mechanismszwithin the nervous system. In most animals the sleep–wakefulness rhythm is coupled to the 24-hour light–dark environment, as are the rest–activity cycles of lower life forms; there is no sharp demarcation between creatures which can be said simply to have rest phases and animals which certainly sleep. In animals possessing developed brains there are electrical rhythms that differ in sleep and in wakefulness, being generally slower during sleep.
The biological clock that makes us sleepy every 24 hours means that shift workers and those who have just flown to different time zones are often tired and inefficient while they are trying to be alert (see jet lag). If it is a long time since we last slept then that too makes us sleepy. Monotony, warmth, restricted movement, and a sense of waiting for something that cannot happen yet — all of these make us sleepy. A sleeplike state of 'animal hypnosis' can also follow extreme stimulation.
The amount of sleep each species takes is proportional to the need for restoration, i.e. to the waking metabolic rate, but is in part also determined by predator status: those animals who sleep safely sleep longer. Among human beings there are wide variations. A few are happy and healthy with under three hours' sleep a night; a minority of others will take as many as ten hours. In general those who habitually sleep longer have shorter reaction times and higher body temperatures by day. Infants sleep a lot, but the sleep of ageing people becomes more and more broken with the years. A person sleeps less if he gets thin and sleeps longer if he gets fat.
There are two kinds of sleep that in man alternate with each other about every 100 minutes. Orthodox sleep (non-rapid eye movement, or NREM, sleep) occupies 80 per cent of the night, and paradoxical sleep (rapid eye movement, or REM, sleep) about 20 per cent. The amount of paradoxical sleep is greater in the newborn, but in adults is proportional to body weight, and among mental defectives to intelligence. It is diminished by anxiety and by many drugs.
Neither of the two kinds of sleep should be thought of as deeper than the other: they are different. Mental life continues in both, but whereas awakenings from orthodox sleep and questions about preceding mental life generally lead to reports of 'thinking', awakenings from paradoxical sleep are generally followed by detailed descriptions of 'dreaming'. However, the recall of dreams is much diminished if as little as five minutes of orthodox sleep intervenes prior to awakening. In paradoxical sleep most body muscles are profoundly relaxed and many reflexes are lost, the blood flows faster through the brain than during wakeful rest, and in men the penis is erect.
Talking may also occur in both kinds of sleep, and reports made after prompt awakenings show concordance between the words and what was being thought or dreamt about. Sleepwalking (see somnambulism) and 'night terrors' arise from orthodox sleep early in the night, as do most episodes of bedwetting. The shriekings of a night terror often occur with sleepwalking, and liability to them runs in families. They are never remembered in the morning.
Indeed, memory of the events of sleep is always very poor. 'Sleep learning' by means of a tape recorder playing lessons all night is ineffective: although what has been heard while still awake may be remembered, nothing of what was played during sleep will be recalled; to remember we must have paid attention, and in sleep we do not pay attention. Even so, sleep is important for memory. If a list of nonsense words is learned, and memory of them is tested 8 hours or 24 hours later, more of the list will be remembered after 24 hours, given an intervening period of sleep, than after 8 hours without sleep. It seems that memory traces are strengthened during sleep, maybe especially by paradoxical sleep, and, since they presumably depend upon the durable molecules of brain protein, this can be understood.
Protein synthesis is favoured by sleep and so sleep enhances growth and restoration. Tissues such as the skin are restored by growth of new cells, and this growth proceeds faster during sleep. Throughout the body's tissues there are protein molecules being broken down and being synthesized all the time. There is a 24-hour variation in the rate of synthesis, the rate being fastest during the period of rest and sleep. In the cerebral cortex, and the retina, protein synthesis is faster during sleep, and in the anterior pituitary there are more cell divisions. The fact that the balance shifts away from degradation towards greater net protein synthesis is a consequence of a lower rate of cellular work during sleep.
In higher animals there are hormones that reinforce the more fundamental effect of the lower rate of cellular work. In man, growth hormone is specifically released by orthodox sleep with the largest continuous slow electrical brain rhythms ('slow wave sleep': see electroencephalography). Growth hormone promotes protein synthesis. On the other hand, adrenaline (epinephrine) and corticosteroids are hormones which are plentiful during wakefulness and which increase protein breakdown. In the blood during sleep, these latter hormones are diminished, and that means that the growth hormone is even more effective. Slow wave sleep is not merely the time of growth-hormone release, it is the time when responsiveness to meaningful sounds or to an itchy skin is minimal, when the body's oxygen consumption is lowest, and cellular work is lowest, and therefore slow wave sleep is 'worth more' than lighter (more responsive) stages of orthodox sleep. If there is a greater need for restoration, as after sleep deprivation, or after an athlete has trained hard, then the next night there is a higher proportion of slow wave sleep and extra growth hormone.
Sleep deprivation causes sleepiness. It is difficult to keep awake anyone who has been deprived of sleep for 60 hours. Such a person has frequent 'microsleeps' and recurrently fails to notice things he ought to notice, being unable to sustain a high level of attention. Sometimes visual illusions or hallucinations are experienced or the individual becomes paranoid. After about 240 hours there are signs of adaptation to a more uniform but inert and dulled state.
People who complain of lack of sleep (insomnia) actually sleep more than they suppose. Indeed, the most distinguishing feature of their sleep is the degree to which it exceeds their own estimates — but we cannot yet measure its relative restorative value. Complaints are commonest among women, among those of nervous temperament, and among older people, and it is they who account for most of the sleeping pills consumed. Although most sleeping pills today belong to the benzodiazepine class and are safe and effective, prolonged use leads to dependence, and attempts to stop them are accompanied by heightened anxiety, nightmares, and poor sleep for a week or two. Regular physical exercise, a good-quality, firm mattress, a warm but ventilated room, a malted milk drink, and sexual satisfaction at bedtime — all these promote good sleep, but they will not cure everyone's complaints. It has to be accepted that broken sleep is as normal a part of growing older as are grey hairs or wrinkles, though insomnia of sudden onset can be the result of mental depression, an illness amenable to treatment.
Finally, let it be emphasized that sleep is not a slothful habit. Its study as a necessity encompasses the whole functioning of the body and, with the study of dreams, some of the mind's most intriguing qualities.
(Published 1987)
The biological clock that makes us sleepy every 24 hours means that shift workers and those who have just flown to different time zones are often tired and inefficient while they are trying to be alert (see jet lag). If it is a long time since we last slept then that too makes us sleepy. Monotony, warmth, restricted movement, and a sense of waiting for something that cannot happen yet — all of these make us sleepy. A sleeplike state of 'animal hypnosis' can also follow extreme stimulation.
The amount of sleep each species takes is proportional to the need for restoration, i.e. to the waking metabolic rate, but is in part also determined by predator status: those animals who sleep safely sleep longer. Among human beings there are wide variations. A few are happy and healthy with under three hours' sleep a night; a minority of others will take as many as ten hours. In general those who habitually sleep longer have shorter reaction times and higher body temperatures by day. Infants sleep a lot, but the sleep of ageing people becomes more and more broken with the years. A person sleeps less if he gets thin and sleeps longer if he gets fat.
There are two kinds of sleep that in man alternate with each other about every 100 minutes. Orthodox sleep (non-rapid eye movement, or NREM, sleep) occupies 80 per cent of the night, and paradoxical sleep (rapid eye movement, or REM, sleep) about 20 per cent. The amount of paradoxical sleep is greater in the newborn, but in adults is proportional to body weight, and among mental defectives to intelligence. It is diminished by anxiety and by many drugs.
Neither of the two kinds of sleep should be thought of as deeper than the other: they are different. Mental life continues in both, but whereas awakenings from orthodox sleep and questions about preceding mental life generally lead to reports of 'thinking', awakenings from paradoxical sleep are generally followed by detailed descriptions of 'dreaming'. However, the recall of dreams is much diminished if as little as five minutes of orthodox sleep intervenes prior to awakening. In paradoxical sleep most body muscles are profoundly relaxed and many reflexes are lost, the blood flows faster through the brain than during wakeful rest, and in men the penis is erect.
Talking may also occur in both kinds of sleep, and reports made after prompt awakenings show concordance between the words and what was being thought or dreamt about. Sleepwalking (see somnambulism) and 'night terrors' arise from orthodox sleep early in the night, as do most episodes of bedwetting. The shriekings of a night terror often occur with sleepwalking, and liability to them runs in families. They are never remembered in the morning.
Indeed, memory of the events of sleep is always very poor. 'Sleep learning' by means of a tape recorder playing lessons all night is ineffective: although what has been heard while still awake may be remembered, nothing of what was played during sleep will be recalled; to remember we must have paid attention, and in sleep we do not pay attention. Even so, sleep is important for memory. If a list of nonsense words is learned, and memory of them is tested 8 hours or 24 hours later, more of the list will be remembered after 24 hours, given an intervening period of sleep, than after 8 hours without sleep. It seems that memory traces are strengthened during sleep, maybe especially by paradoxical sleep, and, since they presumably depend upon the durable molecules of brain protein, this can be understood.
Protein synthesis is favoured by sleep and so sleep enhances growth and restoration. Tissues such as the skin are restored by growth of new cells, and this growth proceeds faster during sleep. Throughout the body's tissues there are protein molecules being broken down and being synthesized all the time. There is a 24-hour variation in the rate of synthesis, the rate being fastest during the period of rest and sleep. In the cerebral cortex, and the retina, protein synthesis is faster during sleep, and in the anterior pituitary there are more cell divisions. The fact that the balance shifts away from degradation towards greater net protein synthesis is a consequence of a lower rate of cellular work during sleep.
In higher animals there are hormones that reinforce the more fundamental effect of the lower rate of cellular work. In man, growth hormone is specifically released by orthodox sleep with the largest continuous slow electrical brain rhythms ('slow wave sleep': see electroencephalography). Growth hormone promotes protein synthesis. On the other hand, adrenaline (epinephrine) and corticosteroids are hormones which are plentiful during wakefulness and which increase protein breakdown. In the blood during sleep, these latter hormones are diminished, and that means that the growth hormone is even more effective. Slow wave sleep is not merely the time of growth-hormone release, it is the time when responsiveness to meaningful sounds or to an itchy skin is minimal, when the body's oxygen consumption is lowest, and cellular work is lowest, and therefore slow wave sleep is 'worth more' than lighter (more responsive) stages of orthodox sleep. If there is a greater need for restoration, as after sleep deprivation, or after an athlete has trained hard, then the next night there is a higher proportion of slow wave sleep and extra growth hormone.
Sleep deprivation causes sleepiness. It is difficult to keep awake anyone who has been deprived of sleep for 60 hours. Such a person has frequent 'microsleeps' and recurrently fails to notice things he ought to notice, being unable to sustain a high level of attention. Sometimes visual illusions or hallucinations are experienced or the individual becomes paranoid. After about 240 hours there are signs of adaptation to a more uniform but inert and dulled state.
People who complain of lack of sleep (insomnia) actually sleep more than they suppose. Indeed, the most distinguishing feature of their sleep is the degree to which it exceeds their own estimates — but we cannot yet measure its relative restorative value. Complaints are commonest among women, among those of nervous temperament, and among older people, and it is they who account for most of the sleeping pills consumed. Although most sleeping pills today belong to the benzodiazepine class and are safe and effective, prolonged use leads to dependence, and attempts to stop them are accompanied by heightened anxiety, nightmares, and poor sleep for a week or two. Regular physical exercise, a good-quality, firm mattress, a warm but ventilated room, a malted milk drink, and sexual satisfaction at bedtime — all these promote good sleep, but they will not cure everyone's complaints. It has to be accepted that broken sleep is as normal a part of growing older as are grey hairs or wrinkles, though insomnia of sudden onset can be the result of mental depression, an illness amenable to treatment.
Finally, let it be emphasized that sleep is not a slothful habit. Its study as a necessity encompasses the whole functioning of the body and, with the study of dreams, some of the mind's most intriguing qualities.
(Published 1987)
— Ian Oswald
- Bibliography
- Adam, K., and Oswald, I. (1983). 'Protein synthesis, bodily renewal and the sleep–wake cycle'. Clinical Science, 65.
- Kety, S. S., Evarts, E. V., and Williams, H. L. (eds.) (1967). Sleep and Altered States of Consciousness.
- Luce, G. G., and Segal, J. (1970). Insomnia.
- Oram, J., and Barnes, C. D. (eds.) (1980). Physiology in Sleep.
- Oswald, I. (1980). Sleep.
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sleep
IN BRIEF: A natural time of rest, usually done at night in a bed.
The cat loves to sleep in front of the fire.
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sleep
sign description: The open hand is held toward the face. The fingers close down as the head tilts foward and the eyes close.
Quotes About:
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Sleep
Quotes:
"The repose of sleep refreshes only the body. It rarely sets the soul at rest. The repose of the night does not belong to us. It is not the possession of our being. Sleep opens within us an inn for phantoms. In the morning we must sweep out the shadows."
- Gaston Bachelard
"Sleep demands of us a guilty immunity. There is not one of us who, given an eternal incognito, a thumbprint nowhere set against our souls, would not commit rape, murder and all abominations."
- Djuna Barnes
"There is between sleep and us something like a pact, a treaty with no secret clauses, and according to this convention it is agreed that, far from being a dangerous, bewitching force, sleep will become domesticated and serve as an instrument of our power to act. We surrender to sleep, but in the way that the master entrusts himself to the slave who serves him."
- Maurice Blanchot
"We term sleep a death by which we may be literally said to die daily; in fine, so like death, I dare not trust it without my prayers."
- Sir Thomas Browne
"Sleep hath its own world, and a wide realm of wild reality. And dreams in their development have breath, and tears, and tortures, and the touch of joy."
- Lord Byron
"Now blessings light on him that first invented this same sleep: it covers a man all over, thoughts and all, like a cloak; 'Tis meat for the hungry, drink for the thirsty, heat for the cold, and cold for the hot. 'Tis the current coin that purchases all the pleasures of the world cheap; and the balance that sets the king and the shepherd, the fool and the wise-man even. There is only one thing that I dislike in sleep; 'Tis that it resembles death; there's very little difference between a man in his first sleep, and a man in his last sleep."
- Miguel De Cervantes
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Sleeping
Dreaming of sleeping may indicate that the dreamer's life is peaceful. Alternatively, it may mean the dreamer is not fully aware of conditions and needs to "wake up and smell the coffee."
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noun
noun, orig US
A prison sentence, usu. comparatively short. (1911 —) .
J. Phelan I wasn't interested myself [in escaping]. Three years was nothing—just a sleep, as you chaps put it (1938).
noun, orig US
A prison sentence, usu. comparatively short. (1911 —) .
J. Phelan I wasn't interested myself [in escaping]. Three years was nothing—just a sleep, as you chaps put it (1938).
| sledging, sleb, sleazoid | |
| sleeping dictionary, sleeve, sleigh-ride |
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A period of rest during which volition and consciousness are in partial or complete abeyance and the bodily functions partially suspended; a behavioral state marked by characteristic immobile posture and diminished but readily reversible sensitivity to external stimuli.
- s. deprivation — caused in animals by constant stimulation, e.g. preventing them from lying down, is followed by a compensatory period of prolonged sleep whenever the opportunity arises.
- s. disorders — see narcolepsy, cataplexy.
- put to s. — a common euphemism for euthanasia.
- rapid eye movement s. — that type of sleep characterized by low voltage but fast electroencephalographic activity and little muscular activity except of the ocular muscles. Believed to be the critical or necessary component of sleep. Called also ‘sleep of the body’ and paradoxical sleep. Called also REM.
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n
A period of rest for the body and mind, during which volition and consciousness are in partial or complete abeyance and the bodily functions partially suspended.
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categories related to 'sleep'
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"Waking up" redirects here. For other uses, see Waking Up (disambiguation).
This article is about sleep in general; for specifically non-human sleep see Sleep (non-human); for other uses, see Sleep (disambiguation).
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles.[1] It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than being in hibernation or a coma. Sleep is a heightened anabolic state, accentuating the growth and rejuvenation of the immune, nervous, skeletal and muscular systems. It is observed in all mammals, all birds, and many reptiles, amphibians, and fish.
The purposes and mechanisms of sleep are only partially clear and are the subject of intense research.[2] Sleep is often thought to help conserve energy,[3][4] but decreases metabolism only about 5–10%.[3][4] Hibernating animals need to sleep despite the hypometabolism seen in hibernation, and must return from hypothermia to euthermia in order to sleep, making sleeping "energetically expensive."[5]
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Contents
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Physiology
Sleep stages
In mammals and birds, sleep is divided into two broad types: rapid eye movement (REM) and non-rapid eye movement (NREM or non-REM) sleep. Each type has a distinct set of associated physiological, neurological, and psychological features. The American Academy of Sleep Medicine (AASM) further divides NREM into three stages: N1, N2, and N3, the last of which is also called delta sleep or slow-wave sleep (SWS).[6]
Sleep proceeds in cycles of REM and NREM, the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the sleep cycle, while the proportion of REM sleep increases later in the sleep cycle and just before natural awakening.
The stages of sleep were first described in 1937 by Alfred Lee Loomis and his coworkers, who separated the different electroencephalography (EEG) features of sleep into five levels (A to E), which represented the spectrum from wakefulness to deep sleep.[7] In 1953, REM sleep was discovered as distinct, and thus William Dement and Nathaniel Kleitman reclassified sleep into four NREM stages and REM.[8] The staging criteria were standardized in 1968 by Allan Rechtschaffen and Anthony Kales in the "R&K sleep scoring manual."[9] In the R&K standard, NREM sleep was divided into four stages, with slow-wave sleep comprising stages 3 and 4. In stage 3, delta waves made up less than 50% of the total wave patterns, while they made up more than 50% in stage 4. Furthermore, REM sleep was sometimes referred to as stage 5.
In 2004, the AASM commissioned the AASM Visual Scoring Task Force to review the R&K scoring system. The review resulted in several changes, the most significant being the combination of stages 3 and 4 into Stage N3. The revised scoring was published in 2007 as The AASM Manual for the Scoring of Sleep and Associated Events.[10] Arousals and respiratory, cardiac, and movement events were also added.[11][12]
Sleep stages and other characteristics of sleep are commonly assessed by polysomnography in a specialized sleep laboratory. Measurements taken include EEG of brain waves, electrooculography (EOG) of eye movements, and electromyography (EMG) of skeletal muscle activity. In humans, the average length of the first sleep cycle is approximately 90 minutes and 100 to 120 minutes from the second to the fourth cycle, which is usually the last one.[13] Each stage may have a distinct physiological function and this can result in sleep that exhibits loss of consciousness but does not fulfill its physiological functions (i.e., one may still feel tired after apparently sufficient sleep).
Scientific studies on sleep have shown that sleep stage at awakening is an important factor in amplifying sleep inertia. Alarm clocks involving sleep stage monitoring appeared on the market in 2005.[14] Using sensing technologies such as EEG electrodes or accelerometers, these alarm clocks are supposed to wake people only from light sleep.
NREM sleep
Main article: Non-rapid eye movement sleep
According to the 2007 AASM standards, NREM consists of three stages. There is relatively little dreaming in NREM.
Stage N1 refers to the transition of the brain from alpha waves having a frequency of 8–13 Hz (common in the awake state) to theta waves having a frequency of 4–7 Hz. This stage is sometimes referred to as somnolence or drowsy sleep. Sudden twitches and hypnic jerks, also known as positive myoclonus, may be associated with the onset of sleep during N1. Some people may also experience hypnagogic hallucinations during this stage. During N1, the subject loses some muscle tone and most conscious awareness of the external environment.
Stage N2 is characterized by sleep spindles ranging from 11 to 16 Hz (most commonly 12–14 Hz) and K-complexes. During this stage, muscular activity as measured by EMG decreases, and conscious awareness of the external environment disappears. This stage occupies 45–55% of total sleep in adults.
Stage N3 (deep or slow-wave sleep) is characterized by the presence of a minimum of 20% delta waves ranging from 0.5–2 Hz and having a peak-to-peak amplitude >75 μV. (EEG standards define delta waves to be from 0 to 4 Hz, but sleep standards in both the original R&K, as well as the new 2007 AASM guidelines have a range of 0.5–2 Hz.) This is the stage in which parasomnias such as night terrors, nocturnal enuresis, sleepwalking, and somniloquy occur. Many illustrations and descriptions still show a stage N3 with 20–50% delta waves and a stage N4 with greater than 50% delta waves; these have been combined as stage N3.
REM sleep
Main article: Rapid eye movement sleep
Rapid eye movement sleep, or REM sleep (also known as paradoxical sleep), accounts for 20–25% of total sleep time in most human adults. The criteria for REM sleep include rapid eye movements as well as a rapid low-voltage EEG. Most memorable dreaming occurs in this stage. At least in mammals, a descending muscular atonia is seen. Such paralysis may be necessary to protect organisms from self-damage through physically acting out scenes from the often-vivid dreams that occur during this stage.
Timing
Sleep timing is controlled by the circadian clock, sleep-wake homeostasis, and in humans, within certain bounds, willed behavior. The circadian clock—an inner timekeeping, temperature-fluctuating, enzyme-controlling device—works in tandem with adenosine, a neurotransmitter that inhibits many of the bodily processes associated with wakefulness. Adenosine is created over the course of the day; high levels of adenosine lead to sleepiness[citation needed]. In diurnal animals, sleepiness occurs as the circadian element causes the release of the hormone melatonin and a gradual decrease in core body temperature. The timing is affected by one's chronotype. It is the circadian rhythm that determines the ideal timing of a correctly structured and restorative sleep episode.[15]
Homeostatic sleep propensity (the need for sleep as a function of the amount of time elapsed since the last adequate sleep episode) must be balanced against the circadian element for satisfactory sleep.[16] Along with corresponding messages from the circadian clock, this tells the body it needs to sleep.[17] Sleep offset (awakening) is primarily determined by circadian rhythm. A person who regularly awakens at an early hour will generally not be able to sleep much later than his or her normal waking time, even if moderately sleep-deprived.
Sleep duration is affected by the gene DEC2. Some people have a mutation of this gene; they sleep two hours less than normal. Neurology professor Ying-Hui Fu and her colleagues bred mice that carried the DEC2 mutation and slept less than normal mice.[18][19]
Optimal amount in humans
Adult
The optimal amount of sleep is not a meaningful concept unless the timing of that sleep is seen in relation to an individual's circadian rhythms. A person's major sleep episode is relatively inefficient and inadequate when it occurs at the "wrong" time of day; one should be asleep at least six hours before the lowest body temperature.[20] The timing is correct when the following two circadian markers occur after the middle of the sleep episode and before awakening:[21]
- maximum concentration of the hormone melatonin, and
- minimum core body temperature.
For more information on the human circadian rhythm and body temperature, see Biological markers (in the article Circadian rhythm).
Human sleep needs can vary by age and among individuals, and sleep is considered to be adequate when there is no daytime sleepiness or dysfunction. Moreover, self-reported sleep duration is only moderately correlated with actual sleep time as measured by actigraphy,[22] and those affected with sleep state misperception may typically report having slept only four hours despite having slept a full eight hours.[23]
A University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night.[24] Another study of sleep duration and mortality risk in women showed similar results.[25] Other studies show that "sleeping more than 7 to 8 hours per day has been consistently associated with increased mortality," though this study suggests the cause is probably other factors such as depression and socioeconomic status, which would correlate statistically.[26] It has been suggested that the correlation between lower sleep hours and reduced morbidity only occurs with those who wake naturally, rather than those who use an alarm.
Researchers at the University of Warwick and University College London have found that lack of sleep can more than double the risk of death from cardiovascular disease, but that too much sleep can also be associated with a doubling of the risk of death, though not primarily from cardiovascular disease.[28][29] Professor Francesco Cappuccio said, "Short sleep has been shown to be a risk factor for weight gain, hypertension, and Type 2 diabetes, sometimes leading to mortality; but in contrast to the short sleep-mortality association, it appears that no potential mechanisms by which long sleep could be associated with increased mortality have yet been investigated. Some candidate causes for this include depression, low socioeconomic status, and cancer-related fatigue... In terms of prevention, our findings indicate that consistently sleeping around seven hours per night is optimal for health, and a sustained reduction may predispose to ill health."
Furthermore, sleep difficulties are closely associated with psychiatric disorders such as depression, alcoholism, and bipolar disorder.[30] Up to 90% of adults with depression are found to have sleep difficulties. Dysregulation found on EEG includes disturbances in sleep continuity, decreased delta sleep and altered REM patterns with regard to latency, distribution across the night and density of eye movements.[31]
Hours by age
Children need more sleep per day in order to develop and function properly: up to 18 hours for newborn babies, with a declining rate as a child ages.[17] A newborn baby spends almost 9 hours a day in REM sleep. By the age of five or so, only slightly over two hours is spent in REM. Studies say that school age children need about 10 to 11 hours of sleep.[32]
| Age and condition | Sleep Needs |
|---|---|
| Newborns (0–2 months) | 12 to 18 hours[33] |
| Infants (3–11 months) | 14 to 15 hours[33] |
| Toddlers (1–3 years) | 12 to 14 hours[33] |
| Preschoolers (3–5 years) | 11 to 13 hours[33] |
| School-age children (5–10 years) | 10 to 11 hours[33] |
| Adolescents (10–17 years) | 8.5 to 9.25 hours[33][34] |
| Adults, including elderly | 7 to 9 hours[33] |
| Pregnant women | 8(+) hours |
Siesta or nap
The siesta habit has recently been associated with a 37% reduction in coronary mortality, possibly due to reduced cardiovascular stress mediated by daytime sleep.[35] Nevertheless, epidemiological studies on the relations between cardiovascular health and siesta have led to conflicting conclusions, possibly because of poor control of moderator variables, such as physical activity. It is possible that people who take a siesta have different physical activity habits, e.g., waking earlier and scheduling more activity during the morning. Such differences in physical activity may mediate different 24-hour profiles in cardiovascular function. Even if such effects of physical activity can be discounted for explaining the relationship between siesta and cardiovascular health, it is still unknown whether it is the daytime nap itself, a supine posture or the expectancy of a nap that is the most important factor. It was recently suggested that a short nap can reduce stress and blood pressure (BP), with the main changes in BP occurring between the time of lights off and the onset of stage 1.[36][37] Dr. Zaregarizi and his team have conducted that the acute time of falling asleep was where beneficial cardiovascular changes take place. This study has indicated that a large decline in blood pressure occurs during the daytime sleep-onset period only when sleep is expected however when subjects rest in a supine position, the same reduction in blood pressure is not observed. This blood pressure reduction may be associated with the lower coronary mortality rates seen in Mediterranean and Latin American populations where siestas are common. Dr. Zaregarizi assessed cardiovascular function (blood pressure, heart rate, and measurements of blood vessel dilation) while nine healthy volunteers, 34 years of age on average, spent an hour standing quietly; reclining at rest but not sleeping; or reclining to nap. All participants were restricted to 4 hours of sleep on the night prior to each of the sleep laboratory tests. During the three phases of daytime sleep, he noted significant reductions in blood pressure and heart rate. By contrast, they did not observe changes in cardiovascular function while the participants were standing or reclining at rest. These findings also show that the greatest decline in blood pressure occurs between lights-off and onset of daytime sleep itself. During this sleep period, which lasted 9.7 minutes on average, blood pressure decreased, while blood vessel dilation increased by more than 9 percent. “There is little change in blood pressure once a subject is actually asleep," Dr. Zaregarizi noted, and he found minor changes in blood vessel dilation during sleep.[36][37]
Sleep debt
Main article: Sleep debt
Sleep debt is the effect of not getting enough sleep; a large debt causes mental, emotional and physical fatigue.
Sleep debt results in diminished abilities to perform high-level cognitive functions. Neurophysiological and functional imaging studies have demonstrated that frontal regions of the brain are particularly responsive to homeostatic sleep pressure.[38]
Scientists do not agree on how much sleep debt it is possible to accumulate; whether it is accumulated against an individual's average sleep or some other benchmark; nor on whether the prevalence of sleep debt among adults has changed appreciably in the industrialized world in recent decades. It is likely that children are sleeping less than previously in Western societies.[39]
Genetics
It is suspected that a considerable amount of sleep-related behavior, such as when and how long a person needs to sleep, is regulated by our genetics. Researchers have discovered some evidence that seems to support this assumption.[40] ABCC9 is one gene found to be potentially significant.[citation needed]
Functions
The multiple theories proposed to explain the function of sleep reflect the as-yet incomplete understanding of the subject. (When asked, after 50 years of research, what he knew about the reason people sleep William Dement, founder of Stanford University's Sleep Research Center, answered, "As far as I know, the only reason we need to sleep that is really, really solid is because we get sleepy."[41]) It is likely that sleep evolved to fulfill some primeval function and took on multiple functions over time[citation needed] (analogous to the larynx, which controls the passage of food and air, but descended over time to develop speech capabilities).
If sleep were not essential, one would expect to find:
- Animal species that do not sleep at all
- Animals that do not need recovery sleep when they stay awake longer than usual
- Animals that suffer no serious consequences as a result of lack of sleep
Outside of a few basal animals that have no brain or a very simple one, no animals have been found to date that satisfy any of these criteria.[42] While some varieties of shark, such as great whites and hammerheads, must remain in motion at all times to move oxygenated water over their gills, it is possible they still sleep one cerebral hemisphere at a time as marine mammals do. However it remains to be shown definitively whether any fish is capable of unihemispheric sleep.
Some of the many proposed functions of sleep are as follows:
Restoration
Wound healing has been shown to be affected by sleep. A study conducted by Gumustekin et al.[43] in 2004 shows sleep deprivation hindering the healing of burns on rats.
It has been shown that sleep deprivation affects the immune system. In a study by Zager et al. in 2007,[44] rats were deprived of sleep for 24 hours. When compared with a control group, the sleep-deprived rats' blood tests indicated a 20% decrease in white blood cell count, a significant change in the immune system. It is now possible to state that "sleep loss impairs immune function and immune challenge alters sleep," and it has been suggested that mammalian species which invest in longer sleep times are investing in the immune system, as species with the longer sleep times have higher white blood cell counts.[45] Sleep has also been theorized to effectively combat the accumulation of free radicals in the brain, by increasing the efficiency of endogeneous antioxidant mechanisms.[46]
It has yet to be proven that sleep duration affects somatic growth. One study by Jenni et al.[47] in 2007 recorded growth, height, and weight, as correlated to parent-reported time in bed in 305 children over a period of nine years (age 1–10). It was found that "the variation of sleep duration among children does not seem to have an effect on growth." It has been shown that sleep—more specifically, slow-wave sleep (SWS)—does affect growth hormone levels in adult men. During eight hours' sleep, Van Cauter, Leproult, and Plat[48] found that the men with a high percentage of SWS (average 24%) also had high growth hormone secretion, while subjects with a low percentage of SWS (average 9%) had low growth hormone secretion.
There are multiple arguments supporting the restorative function of sleep. The metabolic phase during sleep is anabolic; anabolic hormones such as growth hormones (as mentioned above) are secreted preferentially during sleep. The duration of sleep among species is, in general, inversely related to animal size[citation needed] and directly related to basal metabolic rate. Rats with a very high basal metabolic rate sleep for up to 14 hours a day, whereas elephants and giraffes with lower BMRs sleep only 3–4 hours per day.
Energy conservation could as well have been accomplished by resting quiescent without shutting off the organism from the environment, potentially a dangerous situation. A sedentary nonsleeping animal is more likely to survive predators, while still preserving energy. Sleep, therefore, seems to serve another purpose, or other purposes, than simply conserving energy; for example, hibernating animals waking up from hibernation go into rebound sleep because of lack of sleep during the hibernation period. They are definitely well-rested and are conserving energy during hibernation, but need sleep for something else.[5] Rats kept awake indefinitely develop skin lesions, hyperphagia, loss of body mass, hypothermia, and, eventually, fatal sepsis.[49]
Ontogenesis
According to the ontogenetic hypothesis of REM sleep, the activity occurring during neonatal REM sleep (or active sleep) seems to be particularly important to the developing organism (Marks et al., 1995). Studies investigating the effects of deprivation of active sleep have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass (Mirmiran et al., 1983), and an abnormal amount of neuronal cell death.[50]
REM sleep appears to be important for development of the brain. REM sleep occupies the majority of time of sleep of infants, who spend most of their time sleeping. Among different species, the more immature the baby is born, the more time it spends in REM sleep. Proponents also suggest that REM-induced muscle inhibition in the presence of brain activation exists to allow for brain development by activating the synapses, yet without any motor consequences that may get the infant in trouble. Additionally, REM deprivation results in developmental abnormalities later in life.
However, this does not explain why older adults still need REM sleep. Aquatic mammal infants do not have REM sleep in infancy;[51] REM sleep in those animals increases as they age.
Memory processing
Scientists have shown numerous ways in which sleep is related to memory. In a study conducted by Turner, Drummond, Salamat, and Brown,[52] working memory was shown to be affected by sleep deprivation. Working memory is important because it keeps information active for further processing and supports higher-level cognitive functions such as decision making, reasoning, and episodic memory. The study allowed 18 women and 22 men to sleep only 26 minutes per night over a four-day period. Subjects were given initial cognitive tests while well-rested, and then were tested again twice a day during the four days of sleep deprivation. On the final test, the average working memory span of the sleep-deprived group had dropped by 38% in comparison to the control group.
Memory seems to be affected differently by certain stages of sleep such as REM and slow-wave sleep (SWS). In one study,[53] multiple groups of human subjects were used: wake control groups and sleep test groups. Sleep and wake groups were taught a task and were then tested on it, both on early and late nights, with the order of nights balanced across participants. When the subjects' brains were scanned during sleep, hypnograms revealed that SWS was the dominant sleep stage during the early night, representing around 23% on average for sleep stage activity. The early-night test group performed 16% better on the declarative memory test than the control group. During late-night sleep, REM became the most active sleep stage at about 24%, and the late-night test group performed 25% better on the procedural memory test than the control group. This indicates that procedural memory benefits from late, REM-rich sleep, whereas declarative memory benefits from early, SWS-rich sleep.
A study conducted by Datta[54] indirectly supports these results. The subjects chosen were 22 male rats. A box was constructed wherein a single rat could move freely from one end to the other. The bottom of the box was made of a steel grate. A light would shine in the box accompanied by a sound. After a five-second delay, an electrical shock would be applied. Once the shock commenced, the rat could move to the other end of the box, ending the shock immediately. The rat could also use the five-second delay to move to the other end of the box and avoid the shock entirely. The length of the shock never exceeded five seconds. This was repeated 30 times for half the rats. The other half, the control group, was placed in the same trial, but the rats were shocked regardless of their reaction. After each of the training sessions, the rat would be placed in a recording cage for six hours of polygraphic recordings. This process was repeated for three consecutive days. This study found that during the posttrial sleep recording session, rats spent 25.47% more time in REM sleep after learning trials than after control trials. These trials support the results of the Born et al. study, indicating an obvious correlation between REM sleep and procedural knowledge.
An observation of the Datta study is that the learning group spent 180% more time in SWS than did the control group during the post-trial sleep-recording session. This phenomenon is supported by a study performed by Kudrimoti, Barnes, and McNaughton.[55] This study shows that after spatial exploration activity, patterns of hippocampal place cells are reactivated during SWS following the experiment. In a study by Kudrimoti et al., seven rats were run through a linear track using rewards on either end. The rats would then be placed in the track for 30 minutes to allow them to adjust (PRE), then they ran the track with reward-based training for 30 minutes (RUN), and then they were allowed to rest for 30 minutes. During each of these three periods, EEG data were collected for information on the rats' sleep stages. Kudrimoti et al. computed the mean firing rates of hippocampal place cells during prebehavior SWS (PRE) and three ten-minute intervals in postbehavior SWS (POST) by averaging across 22 track-running sessions from seven rats. The results showed that ten minutes after the trial RUN session, there was a 12% increase in the mean firing rate of hippocampal place cells from the PRE level; however, after 20 minutes, the mean firing rate returned rapidly toward the PRE level. The elevated firing of hippocampal place cells during SWS after spatial exploration could explain why there were elevated levels of SWS sleep in Datta's study, as it also dealt with a form of spatial exploration.
A study has also been done involving direct current stimulation to the prefrontal cortex to increase the amount of slow oscillations during SWSfe. The direct current stimulation greatly enhanced word-pair retention the following day, giving evidence that SWS plays a large role in the consolidation of episodic memories.[56]
The different studies all suggest that there is a correlation between sleep and the complex functions of memory. Harvard sleep researchers Saper[57] and Stickgold[58] point out that an essential part of memory and learning consists of nerve cell dendrites' sending of information to the cell body to be organized into new neuronal connections. This process demands that no external information is presented to these dendrites, and it is suggested that this may be why it is during sleep that memories and knowledge are solidified and organized.
Preservation
The "Preservation and Protection" theory holds that sleep serves an adaptive function. It protects the animal during that portion of the 24-hour day in which being awake, and hence roaming around, would place the individual at greatest risk.[59] Organisms do not require 24 hours to feed themselves and meet other necessities. From this perspective of adaptation, organisms are safer by staying out of harm's way, where potentially they could be prey to other, stronger organisms. They sleep at times that maximize their safety, given their physical capacities and their habitats.
This theory fails to explain why the brain disengages from the external environment during normal sleep. However, the brain consumes a large proportion of the body's calories at any one time and preservation of energy could only occur by limiting its sensory inputs. Another argument against the theory is that sleep is not simply a passive consequence of removing the animal from the environment, but is a "drive"; animals alter their behaviors in order to obtain sleep. Therefore, circadian regulation is more than sufficient to explain periods of activity and quiescence that are adaptive to an organism, but the more peculiar specializations of sleep probably serve different and unknown functions. Moreover, the preservation theory needs to explain why carnivores like lions, which are on top of the food chain and thus have little to fear, sleep the most. It has been suggested that they need to minimize energy expenditure when not hunting.
Preservation also does not explain why aquatic mammals sleep while moving. Quiescence during these vulnerable hours would do the same and would be more advantageous, because the animal would still be able to respond to environmental challenges like predators, etc. Sleep rebound that occurs after a sleepless night will be maladaptive, but obviously must occur for a reason. A zebra falling asleep the day after it spent the sleeping time running from a lion is more, not less, vulnerable to predation.
Dreaming
Main article: Dream
Dreaming is the perceived experience of sensory images and sounds during sleep, in a sequence which the dreamer usually perceives more as an apparent participant than as an observer. Dreaming is stimulated by the pons and mostly occurs during the REM phase of sleep.
People have proposed many hypotheses about the functions of dreaming. Sigmund Freud postulated that dreams are the symbolic expression of frustrated desires that had been relegated to the unconscious mind, and he used dream interpretation in the form of psychoanalysis to uncover these desires. See Freud: The Interpretation of Dreams.
Freud's work concerns the psychological role of dreams, which does not exclude any physiological role they may have. Recent research[60] claims that sleep has the overall role of consolidation and organization of synaptic connections formed during learning and experience. As such, Freud's work is not ruled out. Nevertheless, Freud's research has been expanded on, especially with regard to the organization and consolidation of recent memory.
Certain processes in the cerebral cortex have been studied by John Allan Hobson and Robert McCarley. In their activation synthesis theory, for example, they propose that dreams are caused by the random firing of neurons in the cerebral cortex during the REM period. Neatly, this theory helps explain the irrationality of the mind during REM periods, as, according to this theory, the forebrain then creates a story in an attempt to reconcile and make sense of the nonsensical sensory information presented to it.[61] Ergo, the odd nature of many dreams.
Effect of food and drink on sleep
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Hypnotics
- Nonbenzodiazepine hypnotics such as eszopiclone (Lunesta), zaleplon (Sonata), and zolpidem (Ambien) are commonly used as sleep aids prescribed by doctors to treat forms of insomnia. Nonbenzodiazepines are the most commonly prescribed and OTC sleep aids used worldwide and have been greatly growing in use since the 1990s. They target the GABAA receptor.
- Benzodiazepines target the GABAA receptor also, and as such, they are commonly used sleep aids as well, though benzodiazepines have been found to decrease REM sleep.[62]
- Antihistamines, such as diphenhydramine (Benadryl) and doxylamine (found in various OTC medicines, such as NyQuil)
- Alcohol – Often, people start drinking alcohol in order to get to sleep (alcohol is initially a sedative and will cause somnolence, encouraging sleep).[63] However, being addicted to alcohol can lead to disrupted sleep, because alcohol has a rebound effect later in the night. As a result, there is strong evidence linking alcoholism and forms of insomnia.[64] Alcohol also reduces REM sleep.[62]
- Barbiturates cause drowsiness and have actions similar to alcohol in that they have a rebound effect and inhibit REM sleep, so they are not used as a long-term sleep aid.[65]
- Melatonin is a naturally occurring hormone that regulates sleepiness. It is made in the brain, where tryptophan is converted into serotonin and then into melatonin, which is released at night by the pineal gland to induce and maintain sleep. Melatonin supplementation may be used as a sleep aid, both as a hypnotic and as a chronobiotic (see phase response curve, PRC).
- Siesta and the "post-lunch dip" – Many people have a temporary drop in alertness in the early afternoon, commonly known as the "post-lunch dip." While a large meal can make a person feel sleepy, the post-lunch dip is mostly an effect of the biological clock. People naturally feel most sleepy (have the greatest "drive for sleep") at two times of the day about 12 hours apart—for example, at 2:00 a.m. and 2:00 p.m. At those two times, the body clock "kicks in." At about 2 p.m. (14:00), it overrides the homeostatic buildup of sleep debt, allowing several more hours of wakefulness. At about 2 a.m. (02:00), with the daily sleep debt paid off, it "kicks in" again to ensure a few more hours of sleep.
- Tryptophan – The amino acid tryptophan is a building block of proteins. It has been claimed to contribute to sleepiness, since it is a precursor of the neurotransmitter serotonin, involved in sleep regulation. However, no solid data have ever linked modest dietary changes in tryptophan to changes in sleep.
- Marijuana – Some people use marijuana to induce sleepiness. Users often report relaxation and drowsiness. It has been shown that Tetrahydrocannabinol, the principal psychoactive constituent in marijuana, reduces the amount of REM sleep.[66] Frequent users often report being unable to recall their dreams.
Stimulants
- Amphetamine (dextroamphetamine, and a related, slightly more powerful drug methamphetamine, etc.) are used to treat narcolepsy. Their most common effects are anxiety, insomnia, stimulation, increased alertness, and decreased hunger.
- Caffeine is a stimulant that works by slowing the action of the hormones in the brain that cause somnolence, particularly by acting as an antagonist at adenosine receptors. Effective dosage is individual, in part dependent on prior usage. It can cause a rapid reduction in alertness as it wears off.
- Cocaine and crack cocaine – Studies on cocaine have shown its effects to be mediated through the circadian rhythm system.[67] This may be related to the onset of hypersomnia (oversleeping) in regard to "cocaine-induced sleep disorder."[68]
- MDMA, including similar drugs like MDA, MMDA, or bk-MDMA – The class of drugs called empathogen-entactogens keep users awake with intense euphoria. Commonly known as "ecstasy."
- Methylphenidate – Commonly known by the brand names Ritalin and Concerta, methylphenidate is similar in action to amphetamine and cocaine; its chemical composition more closely resembles that of cocaine.
- Tobacco – Tobacco has been found not only to disrupt but also to reduce total sleep time. In studies, users have described more daytime drowsiness than nonsmokers.[69]
- Other analeptic drugs like Modafinil and Armodafinil are prescribed to treat narcolepsy, hypersomnia, shift work sleep disorder, and other conditions causing Excessive Daytime Sleepiness. The precise mechanism of these CNS stimulants is not known, but they have been shown to increase both the release of monoamines and levels of hypothalamic histamine, thereby promoting wakefulness.
Insomnia
Insomnia is a general term describing difficulty falling asleep and staying asleep. Insomnia can have many different causes, including psychological stress, a poor sleep environment, an inconsistent sleep schedule, or excessive mental or physical stimulation in the hours before bedtime. Insomnia is often treated through behavioral changes like keeping a regular sleep schedule, avoiding stimulating or stressful activities before bedtime, and cutting down on stimulants such as caffeine. Patients are often counseled to improve their sleep environment by installing heavy drapes to shut out all sunlight, and keeping computers, televisions and work materials out of the sleeping area.
A 2010 review of published scientific research suggested that exercise generally improves sleep for most people, and helps sleep disorders such as insomnia. The optimum time to exercise may be 4 to 8 hours before bedtime, though exercise at any time of day is beneficial, with the exception of heavy exercise taken shortly before bedtime, which may disturb sleep. However there is insufficient evidence to draw detailed conclusions about the relationship between exercise and sleep.[70]
Sleeping medications such as Ambien and Lunesta are an increasingly popular treatment for insomnia, and have become a major source of revenue for drug companies. Although these nonbenzodiazepine medications are generally believed to be better and safer than earlier generations of sedatives, they have still generated some controversy and discussion regarding side-effects.
White noise appears to be a promising treatment for insomnia.[71]
Obstructive sleep apnea
Obstructive sleep apnea is a condition in which major pauses in breathing occur during sleep, disrupting the normal progression of sleep and often causing other more severe health problems. Apneas occur when the muscles around the patient's airway relax during sleep, causing the airway to collapse and block the intake of oxygen. As oxygen levels in the blood drop, the patient then comes out of deep sleep in order to resume breathing. When several of these episodes occur per hour, sleep apnea rises to a level of seriousness that may require treatment.
Diagnosing sleep apnea usually requires a professional sleep study performed in a sleep clinic, because the episodes of wakefulness caused by the disorder are extremely brief and patients usually do not remember experiencing them. Instead, many patients simply feel tired after getting several hours of sleep and have no idea why. Major risk factors for sleep apnea include chronic fatigue, old age, obesity and snoring.
Other sleep disorders
Sleep disorders include narcolepsy, periodic limb movement disorder (PLMD), restless leg syndrome (RLS), and the circadian rhythm sleep disorders. Fatal familial insomnia, or FFI, is an extremely rare genetic disease with no known treatment or cure, is characterized by increasing insomnia as one of its symptoms; ultimately sufferers of the disease stop sleeping entirely, before dying of the disease.[41]
Older people are more easily awakened by disturbances in the environment[72] and may to some degree lose the ability to consolidate sleep.
Anthropology of sleep
Research suggests that sleep patterns vary significantly across cultures.[73][74] The most striking differences are between societies that have plentiful sources of artificial light and ones that do not.[73] The primary difference appears to be that pre-light cultures have more broken-up sleep patterns.[73] For example, people might go to sleep far sooner after the sun sets, but then wake up several times throughout the night, punctuating their sleep with periods of wakefulness, perhaps lasting several hours.[73] The boundaries between sleeping and waking are blurred in these societies.[73] Some observers believe that nighttime sleep in these societies is most often split into two main periods, the first characterized primarily by deep sleep and the second by REM sleep.[73]
Some societies display a fragmented sleep pattern in which people sleep at all times of the day and night for shorter periods. In many nomadic or hunter-gatherer societies, people will sleep on and off throughout the day or night depending on what is happening.[73] Plentiful artificial light has been available in the industrialized West since at least the mid-19th century, and sleep patterns have changed significantly everywhere that lighting has been introduced.[73] In general, people sleep in a more concentrated burst through the night, going to sleep much later, although this is not always true.[73] Historian Roger Ekrich thinks that the traditional pattern of "segmented sleep" as it is called began to disappear among the urban upper class in Europe in the late 17th century and the change spread over the next 200 years; by the 1920s "the idea of a first and second sleep had receded entirely from our social consciousness."[75] Ekrich attributes the change to increases in "street lighting, domestic lighting and a surge in coffee houses," which slowly made nighttime a legitimate time for activity, decreasing the time available for rest.[75]
In some societies, people generally sleep with at least one other person (sometimes many) or with animals. In other cultures, people rarely sleep with anyone but a most intimate relation, such as a spouse. In almost all societies, sleeping partners are strongly regulated by social standards. For example, people might only sleep with their immediate family, extended family, spouses, their children, children of a certain age, children of specific gender, peers of a certain gender, friends, peers of equal social rank, or with no one at all. Sleep may be an actively social time, depending on the sleep groupings, with no constraints on noise or activity.[73]
People sleep in a variety of locations. Some sleep directly on the ground; others on a skin or blanket; others sleep on platforms or beds. Some sleep with blankets, some with pillows, some with simple headrests, some with no head support. These choices are shaped by a variety of factors, such as climate, protection from predators, housing type, technology, personal preference, and the incidence of pests.[73]
Sleep in non-humans
Main article: Sleep (non-human)
Neurological sleep states can be difficult to detect in some animals. In these cases, sleep may be defined using behavioral characteristics such as minimal movement, postures typical for the species, and reduced responsiveness to external stimulation. Sleep is quickly reversible, as opposed to hibernation or coma, and sleep deprivation is followed by longer or deeper rebound sleep. Herbivores, who require a long waking period to gather and consume their diet, typically sleep less each day than similarly sized carnivores, who might well consume several days' supply of meat in a sitting.
Horses and other herbivorous ungulates can sleep while standing, but must necessarily lie down for REM sleep (which causes muscular atony) for short periods. Giraffes, for example, only need to lie down for REM sleep for a few minutes at a time. Bats sleep while hanging upside down. Some aquatic mammals and some birds can sleep with one half of the brain while the other half is awake, so-called unihemispheric slow-wave sleep.[76] Birds and mammals have cycles of non-REM and REM sleep (as described above for humans), though birds' cycles are much shorter and they do not lose muscle tone (go limp) to the extent that most mammals do.
Many mammals sleep for a large proportion of each 24-hour period when they are very young.[77] However, killer whales and some dolphins do not sleep during the first month of life.[78] Such differences may be explained by the ability of land-mammal newborns to be easily protected by parents while sleeping, while marine animals must, even while very young, be more continuously vigilant for predators.
See also
- Cortisol awakening response
- Microsleep
- Morvan's syndrome
- Polyphasic sleep
- Power nap
- Segmented sleep
- Sleep architecture
- Sleep medicine
- Somnology
- Sudden infant death syndrome
- Sudden unexpected death syndrome
Positions, practices, and rituals
- Sleeping positions
- Co-sleeping
- Hypnosis
- Meditation
- Neutral spine
- Sleep hygiene
- Yoga-nidra
- World Sleep Day
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- ^ Siegel, Jerome M (1999). "Sleep". Encarta Encyclopedia. Microsoft. Archived from the original on 2007-12-14. http://web.archive.org/web/20071214003754/http://www.npi.ucla.edu/sleepresearch/encarta/Article.htm. Retrieved 2008-01-25.
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- ^ "Backgrounder: Later School Start Times". National Sleep Foundation. Undated. http://www.sleepfoundation.org/article/hot-topics/backgrounder-later-school-start-times. Retrieved 2009-10-02. "Teens are among those least likely to get enough sleep; while they need on average 91⁄4 hours of sleep per night..."
- ^ Naska, A., Oikonomou, E., Trichopoulou, A., Psaltopoulou, T. and Trichopoulos, D. (2007). "Siesta in healthy adults and coronary mortality in the general population". Archives of Internal Medicine 167 (3): 296–301. doi:10.1001/archinte.167.3.296. PMID 17296887. http://archinte.ama-assn.org/cgi/content/full/167/3/296.
- ^ a b Zaregarizi M,et al. Acute changes in cardiovascular function during the onset period of daytime sleep: Comparison to lying awake and standing. doi:10.1152/japplphysiol.00474.2007.
- ^ a b MohammadReza Zaregarizi. Effects of Exercise & Daytime Sleep on Human Haemodynamics: With Focus on Changes in Cardiovascular Function during Daytime Sleep Onset. ISBN 978-3-8484-1726-1.
- ^ Gottselig JM, Adam M, Rétey JV, Khatami R, Achermann P, Landolt HP (March 2006). "Random number generation during sleep deprivation: effects of caffeine on response maintenance and stereotypy". Journal of Sleep Research 15 (1): 31–40. doi:10.1111/j.1365-2869.2006.00497.x. PMID 16490000.
- ^ Iglowstein I, Jenni OG, Molinari L, Largo RH (February 2003). "Sleep duration from infancy to adolescence: reference values and generational trends". Pediatrics 111 (2): 302–7. doi:10.1542/peds.111.2.302. PMID 12563055. "Thus, the shift in the evening bedtime across cohorts accounted for the substantial decrease in sleep duration in younger children between the 1970s and the 1990s... [A] more liberal parental attitude toward evening bedtime in the past decades is most likely responsible for the bedtime shift and for the decline of sleep duration..."
- ^ He, Y.; Jones, C. R.; Fujiki, N.; Xu, Y.; Guo, B.; Holder, J. L.; Rossner, M. J.; Nishino, S. et al (2009). "The Transcriptional Repressor DEC2 Regulates Sleep Length in Mammals". Science 325 (5942): 866–70. doi:10.1126/science.1174443. PMC 2884988. PMID 19679812. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2884988.
- ^ a b Max, D. T. The Secrets of Sleep National Geographic Magazine, May 2010.
- ^ Cirelli, Chiara; Giulio Tononi (August 26, 2008). "Is Sleep Essential?" (Essay). PLoS Biol (Public Library of Science) 6 (8): e216. doi:10.1371/journal.pbio.0060216. PMC 2525690. PMID 18752355. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2525690. "... it would seem that searching for a core function of sleep, particularly at the cellular level, remains a worthwhile exercise"
- ^ Gumustekin, K.; Seven, B.; Karabulut, N.; Aktas, O.; Gursan, N.; Aslan, S.; Keles, M.; Varoglu, E.; Dane, S. (2004). "Effects of sleep deprivation, nicotine, and selenium on wound healing in rats". Int J Neurosci 114 (11): 1433–42. doi:10.1080/00207450490509168. PMID 15636354.
- ^ Zager, A.; Andersen, M.L.; Ruiz, F.S.; Antunes, I.B. and Tufik, S. (2007). "Effects of acute and chronic sleep loss on immune modulation of rats". Regulatory, Integrative and Comparative Physiology 293: R504–R509. doi:10.1152/ajpregu.00105.2007.
- ^ Opp, Mark R (January 2009). "Sleeping to fuel the immune system: mammalian sleep and resistance to parasites" (Full text, Creative Commons Attribution License). BMC Evolutionary Biology (BioMed Central Ltd.) 9: 1471–2148. doi:10.1186/1471-2148-9-8. PMC 2633283. PMID 19134176. http://www.biomedcentral.com/1471-2148/9/8. Retrieved 2009-06-28.
- ^ Reimund, E. (October 1994). "The free radical flux theory of sleep". Medical Hypotheses 45 (4): 231–3. doi:10.1016/0306-9877(94)90071-X. PMID 7838006.
- ^ Jenni, O.G.; Molinari, L.; Caflisch, J.A.; Largo, R.H. (2007). "Sleep duration from ages 1 to 10 years: Variability and stability in comparison with growth". Pediatrics 120 (4): e769–e776. doi:10.1542/peds.2006-3300. PMID 17908734.
- ^ Van Cauter, E.; Leproult, R.; Plat, L. (2000). "Age-related changes in slow-wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men". Journal of the American Medical Association 284 (7): 861–868. doi:10.1001/jama.284.7.861. PMID 10938176.
- ^ Guidelines for the Care and Use of Mammals in Neuroscience and Behavioral Research. Institute for Laboratory Animal Research (ILAR), National Research Council. The National Academies Press. 2003. p. 121. ISBN 978-0-309-08903-6. http://books.nap.edu/openbook.php?record_id=10732&page=121. "Sleep deprivation of over 7 days with the disk-over-water system results in the development of ulcerative skin lesions, hyperphagia, loss of body mass, hypothermia, and eventually septicemia and death in rats (Everson, 1995; Rechtschaffen et al., 1983)."
- ^ Morrissey M, Duntley S, Anch A, Nonneman R (2004). "Active sleep and its role in the prevention of apoptosis in the developing brain". Med Hypotheses 62 (6): 876–9. doi:10.1016/j.mehy.2004.01.014. PMID 15142640.
- ^ Amanda Schaffer (May 27, 2007). "Why do we Sleep?". Slate.com. http://www.slate.com/id/2162475/entry/2162477/. Retrieved 2008-08-23.
- ^ Turner, T.H.; Drummond, S.P.A.; Salamat, J.S.; Brown, G.G. (2007). "Effects of 42 hr sleep deprivation on component processes of verbal working memory". Neuropsychology 21 (6): 787–795. doi:10.1037/0894-4105.21.6.787. PMID 17983292.
- ^ cited in Born, J.; Rasch, J.; Gais, S. (2006). "Sleep to remember". Neuroscientist 12: 410.
- ^ Datta, S. (2000). "Avoidance task training potentiates phasic pontine-wave density in the rat: A mechanism for sleep-dependent plasticity". The Journal of Neuroscience 20 (22): 8607–8613. PMID 11069969.
- ^ Kudrimoti, H.S.; Barnes, C.A.; McNaughton, B.L. (1999). "Reactivation of hippocampal cell assemblies: Effects of behavioral state, experience, and EEG dynamics". The Journal of Neuroscience 19 (10): 4090–4101. PMID 10234037.
- ^ Marshall et al., 2006, as cited in Walker, M.P. (2009). "The Role of Sleep in Cognition and Emotion". Annals of the New York Academy of Sciences 1156: 174.
- ^ Saper, Clifford B.; Scammell, Thomas E.; Lu, Jun (2005). "Hypothalamic regulation of sleep and circadian rhythms". Nature 437 (7063): 1257–63. doi:10.1038/nature04284. PMID 16251950.
- ^ Stickgold, Robert (2005). "Sleep-dependent memory consolidation". Nature 437 (7063): 1272–8. doi:10.1038/nature04286. PMID 16251952.
- ^ New Theory Questions Why We Sleep by Charles Q. Choi, LiveScience.com, Aug 25, 2009.
- ^ Connor, Steve (2009-04-03). "Revealed: why we need a good night's sleep". The Independent. http://www.independent.co.uk/news/science/revealed-why-we-need-a-good-nights-sleep-1661100.html. Retrieved 2010-12-02.
- ^ Hobson, J.A.; McCarley, R. (1977). "The brain as a dream state generator: An activation-synthesis hypothesis of the dream process". American Journal of Psychiatry 134 (12): 1335–1348. PMID 21570.
- ^ a b Lee-chiong, Teofilo (24 April 2008). Sleep Medicine: Essentials and Review. Oxford University Press, USA. p. 52. ISBN 0-19-530659-7. http://books.google.com/?id=s1F_DEbRNMcC&pg=PT52.
- ^ Alcohol and Sleep. Sleepdex.org. Retrieved on 2011-12-01.
- ^ Alcohol and Sleep. Alcoholism.about.com (2011-01-10). Retrieved on 2011-12-01.
- ^ Sleep Medications: Barbituates. Sleepdex.org. Retrieved on 2011-12-01.
- ^ Marijuana, Sleep and Dreams. psychologytoday.com. Retrieved on 2012-02-10.
- ^ Abarca C, Albrecht U, Spanagel R (June 2002). "Cocaine sensitization and reward are under the influence of circadian genes and rhythm". Proceedings of the National Academy of Sciences of the United States of America 99 (13): 9026–30. doi:10.1073/pnas.142039099. PMC 124417. PMID 12084940. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=124417.
- ^ Primary hypersomnia: Diagnostic Features[dead link]
- ^ Causes of Sleep Deprivation Sleep.com.
- ^ Buman, M.P. and King, A.C.: "Exercise as a Treatment to Enhance Sleep", American Journal of Lifestyle Medicine, Nov–Dec 2010.
- ^ López HH, Bracha AS, Bracha HS (2002). "Evidence based complementary intervention for insomnia". Hawaii Med J 61 (9): 192, 213. PMID 12422383. http://cogprints.org/5032/1/2002_H.M.J_White-noise_for_PTSD.pdf.
- ^ How Aging Changes Sleep Patterns by Allison Aubrey. Morning Edition, 3 Aug 2009.
- ^ a b c d e f g h i j k Carol M. Worthman and Melissa K. Melby. "6. Toward a comparative developmental ecology of human sleep" (PDF). A comparative developmental ecology. Emory University. http://webdrive.service.emory.edu/groups/research/lchb/PUBLICATIONS%20Worthman/PUBLICATIONS%20CMW%202002/Ecology%20of%20Human%20sleep.pdf.
- ^ Slumber's Unexplored Landscape. Science News Online (1999-09-25). Retrieved on 2011-12-01.
- ^ a b Hegarty, Stephanie (22 February 2012). "The myth of the eight-hour sleep". BBC News. http://www.bbc.co.uk/news/magazine-16964783. Retrieved 22 February 2012.
- ^ Mukhametova, LM; Supina, AY; Polyakovaa, IG (1977-10-14). "Interhemispheric asymmetry of the electroencephalographic sleep patterns in dolphins". Brain Research 134 (3): 581–584. doi:10.1016/0006-8993(77)90835-6. PMID 902119.
- ^ Faraco, Juliette (2000-08-01). "Re: Are there animals who don't sleep or that sleep very little?". MadSci Network: Zoology. http://www.madsci.org/posts/archives/2000-08/965504574.Zo.r.html. Retrieved 2008-01-25.
- ^ Insomnia Mania: Newborn Mammals Don't Sleep for a Month. LiveScience.com
External links
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Wikimedia Commons has media related to: Sleep |
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Look up sleep in Wiktionary, the free dictionary. |
- NIH.gov, National Center on Sleep Disorders Research
- National Sleep Foundation, information on School Start Time and Sleep at National Sleep Foundation
- HealthySleep.med.harvard.edu, from the Division of Sleep Medicine at Harvard Medical School and WGBH Educational Foundation
- PLOSjournals.org, Is Sleep Essential? by Chiara Cirelli and Giulio Tononi, from the Public Library of Science, Biology
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
Top
Sleep
Dansk (Danish)
n. - søvn
v. intr. - sove
v. tr. - sove, have soveplads til
idioms:
- get off to sleep falde i søvn
- get to sleep falde i søvn, få søvn
- go to sleep falde i søvn, lægge sig til at sove
- last sleep den evige søvn
- let sleeping dogs lie sovende hund skal man ej vække
- lose sleep ligge søvnløs
- put to sleep lægge i seng
- sleep around ligge i med hvem som helst, gå i seng med alle og enhver
- sleep like a log sove som en sten
- sleep of the just de retfærdiges søvn
- sleep off sove ud
- sleep on something sove på noget
- sleep over sove for længe
- sleep together sove sammen
- sleep with gå i seng med
- sleeping accommodation soveplads, natlogi
- sleeping bag sovepose
- sleeping car sovevogn
- sleeping partner passiv kompagnon
- sleeping pill sovepille
Nederlands (Dutch)
slapen, overnachten, slaap, nachtrust
Français (French)
n. - sommeil, (Vét) euthanasie
v. intr. - dormir, coucher
v. tr. - dormir, loger, coucher
idioms:
- get off to sleep aller dormir
- get to sleep s'endormir
- go to sleep s'endormir
- last sleep dernier sommeil
- let sleeping dogs lie il ne faut pas réveiller le chat qui dort
- lose sleep perdre le sommeil
- put to sleep endormir (qn), (Vét) faire piquer (animal)
- sleep around coucher avec n'importe qui
- sleep in faire la grasse matinée, dormir trop tard, (US) être logé sur place
- sleep like a log dormir comme un loir
- sleep off dormir pour faire passer (un mal de tête, etc), cuver (son vin, etc)
- sleep on something (fig) dormir sur qch
- sleep out dormir ou coucher à la belle étoile, (US) ne pas loger sur place (un domestique)
- sleep over passer la nuit, coucher
- sleep together coucher ensemble, dormir ensemble
- sleep with coucher avec
- sleeping accommodation endroit où dormir
- sleeping bag sac de couchage
- sleeping car voiture-lit, wagon-lit
- sleeping partner (GB, Comm) commanditaire
- sleeping pill somnifère
- the sleep of the just sommeil du juste
Deutsch (German)
n. - Schlaf
v. - schlafen
idioms:
- get off to sleep einschlafen
- get to sleep einschlafen
- go to sleep einschlafen, schlaf jetzt!
- last sleep ewiger Schlaf
- let sleeping dogs lie keine Unruhe stiften
- lose sleep Schlaf verlieren
- put to sleep einschläfern
- sleep around herumschlafen
- sleep in im Bett bleiben, im Hause wohnen
- sleep like a log wie ein Stein schlafen
- sleep off ausschlafen
- sleep on something etwas überschlafen
- sleep out im Freien schlafen, nicht im Hause wohnen
- sleep over überschlafen
- sleep together miteinander schlafen
- sleep with schlafen mit
- sleeping accommodation Schlafgelegenheit
- sleeping bag Schlafsack
- sleeping car Schlafwagen
- sleeping partner stiller Teilhaber
- sleeping pill Schlaftablette
- the sleep of the just Schlaf des Gerechten
Ελληνική (Greek)
n. - ύπνος, τσίμπλα
v. - κοιμάμαι
idioms:
- get off to sleep αποκοιμιέμαι
- get to sleep αποκοιμιέμαι
- go to sleep αποκοιμιέμαι, μουδιάζω (για μέλος κ.λπ.)
- last sleep ο αιώνιος ύπνος
- let sleeping dogs lie μη θίγεις τα κακώς κείμενα!
- lose sleep χάνω τον ύπνο μου, ξενυχτώ
- put to sleep βάζω να κοιμηθεί, (για ζώα) χαρίζω ευθανασία
- sleep around (καθομ.) πλαγιάζω με τον πρώτο τυχόντα
- sleep like a log κοιμάμαι σαν μωρό
- sleep of the just ο ύπνος του δικαίου
- sleep off αποδιώχνω με τον ύπνο, κοιμάμαι (ενόσω διαρκεί κάτι), ξεπερνάω με τον ύπνο
- sleep on something αναβάλλω απόφαση για την επομένη
- sleep over ξενοκοιμούμαι
- sleep together πλαγιάζω με, έχω σεξουαλικές σχέσεις με
- sleep with πλαγιάζω με, έχω σεξουαλικές σχέσεις με
- sleeping accommodation χώρος να κοιμηθούν
- sleeping bag υπνόσακος
- sleeping car κλινάμαξα, βαγκόν-λι
- sleeping partner αφανής εταίρος
- sleeping pill υπνωτικό χάπι, χάπι για τον ύπνο
Italiano (Italian)
dormire, pernottare, sonno
idioms:
- get to sleep addormentarsi
- last sleep ultimo sonno
- let sleeping dogs lie non svegliare il can che dorme
- lose sleep perdere il sonno
- put to sleep addormentare
- sleep around andare a letto con tutti
- sleep like a log dormire come un ghiro
- sleep of the just il sonno dei giusti
- sleep off smaltire
- sleep on something dormirci sopra
- sleep over fermarsi a dormire
- sleep together dormire insieme
- sleep with andare a letto con
- sleeping bag sacco a pelo
- sleeping car vagone letto
- sleeping partner socio accomodante
- sleeping pill sonnifero
Português (Portuguese)
n. - período de sono (m), inatividade (f), descanso (m), sossego (m)
v. - dormir, adormecer
idioms:
- get off to sleep fazer criança dormir cantando ou contando estórias
- get to sleep ir para a cama
- go to sleep ir dormir, pegar no sono
- last sleep morte (f), sono eterno (m)
- let sleeping dogs lie evitar mexer em casas de marimbondos
- lose sleep insônia (f)
- put to sleep fazer dormir, matar
- sleep around ser sexualmente promíscuo
- sleep like a log dormir profundamente
- sleep of the just o sono dos justos
- sleep off se livrar, se curar de
- sleep on something consultar o travesseiro, deixar a decisão de algo importante para o dia seguinte
- sleep over festa do pijama (f), dormir em casa de amigos
- sleep together dormir juntos
- sleep with ter relações sexuais com, dormir com
- sleeping bag saco de dormir (m)
- sleeping car vagão cama (m), carro dormitório (m)
- sleeping partner sócio comanditário (m)
- sleeping pill soporífero (m), pílula para dormir (f)
Русский (Russian)
спать, ночевать, предоставлять ночлег, неметь (о конечностях), казаться неподвижным, бездействовать, быть спокойным, притихнуть, сон, спячка, онемение (конечностей)
idioms:
- get off to sleep отходить ко сну, засыпать
- get to sleep уснуть
- go to sleep заснуть, онеметь (о конечностях)
- last sleep вечный сон, смерть
- let sleeping dogs lie не будите спящую собаку
- lose sleep не спать (из-за чего-л.)
- put to sleep "усыпить" (животное)
- sleep around распутничать, спать с кем попало
- sleep like a log спать крепким сном, спать как сурок
- sleep of the just спать сном праведника
- sleep off отоспаться
- sleep on something отложить решение до утра
- sleep over отложить решение до утра
- sleep together сожительствовать
- sleep with иметь сексуальные отношения
- sleeping bag спальный мешок
- sleeping car спальный вагон
- sleeping partner компаньон, активно не участвующий в деле
- sleeping pill снотворная таблетка
Español (Spanish)
n. - sueño
v. intr. - dormir
v. tr. - dormir
idioms:
- get off to sleep conciliar el sueño
- get to sleep conciliar el sueño, lograr dormirse
- go to sleep conciliar el sueño, irse a dormir
- last sleep la muerte
- let sleeping dogs lie no remover un asunto
- lose sleep perder el sueño
- put to sleep adormecer
- sleep around acostarse con todos
- sleep in dormirse
- sleep like a log dormir como un tronco
- sleep off dormir para que desaparezca
- sleep on something consultar algo con la almohada
- sleep out dormir fuera de casa
- sleep over consultar algo con la almohada
- sleep together dormir juntos
- sleep with dormir con
- sleeping accommodation lugar para dormir
- sleeping bag saco de dormir
- sleeping car coche cama
- sleeping partner socio comanditario
- sleeping pill somnífero
- the sleep of the just dormir con la consciencia tranquila, el sueño de los justos, sueño profundo, dormir a pierna suelta
Svenska (Swedish)
n. - sömn
v. - sova, ligga över, dåsa, ha liggplats åt, ordna liggplats åt, ge nattlogi åt, logera, hysa
中文（简体）(Chinese (Simplified))
睡眠, 睡意, 静止, 睡, 睡觉, 静止下来, 保持寂静, 长眠, 安息, 歇夜, 可供...住宿, 用睡眠消除, 以睡眠度过
idioms:
- get off to sleep 睡着
- get to sleep 入睡
- go to sleep 睡着
- last sleep 死, 长眠
- let sleeping dogs lie 莫惹是非
- lose sleep 损失睡眠
- put to sleep 使入睡, 使...无痛苦地处死
- sleep around 乱搞男女关系
- sleep like a log 熟睡
- sleep of the just 心安理得地睡安稳觉, 问心无愧地睡觉
- sleep off 以睡眠来消除...
- sleep on something 把...留到第二天解决
- sleep over 借宿别人处, 忽视, 不注意
- sleep together 一起睡, 有性关系
- sleep with 跟...一起睡, 跟...有性关系
- sleeping accommodation 睡觉的地方
- sleeping bag 睡袋
- sleeping car 铁路之卧车
- sleeping partner 隐名合伙人
- sleeping pill 安眠药
中文（繁體）(Chinese (Traditional))
n. - 睡眠, 睡意, 靜止
v. intr. - 睡, 睡覺, 靜止下來, 保持寂靜, 長眠, 安息, 歇夜
v. tr. - 睡, 可供...住宿, 用睡眠消除, 以睡眠度過
idioms:
- get off to sleep 睡著
- get to sleep 入睡
- go to sleep 睡著
- last sleep 死, 長眠
- let sleeping dogs lie 莫惹是非
- lose sleep 損失睡眠
- put to sleep 使入睡, 使...無痛苦地處死
- sleep around 亂搞男女關係
- sleep like a log 熟睡
- sleep of the just 心安理得地睡安穩覺, 問心無愧地睡覺
- sleep off 以睡眠來消除...
- sleep on something 把...留到第二天解決
- sleep over 借宿別人處, 忽視, 不注意
- sleep together 一起睡, 有性關係
- sleep with 跟...一起睡, 跟...有性關係
- sleeping accommodation 睡覺的地方
- sleeping bag 睡袋
- sleeping car 鐵路之臥車
- sleeping partner 隱名合夥人
- sleeping pill 安眠藥
한국어 (Korean)
n. - 잠자다, 정지, 영면
v. intr. - 잠자다, (기능이) 정지하다, 영원히 죽어 있다
v. tr. - 잠자다, ~을 묵게 하다
idioms:
- get off to sleep 잠들다
- get to sleep 잠들다
- go to sleep 잠자리에 들다, (팔, 다리가) 저리다
- put to sleep 재우다, 마취시키다, 죽이다
- sleep around 여러 남자(여자)와 자다
- sleep off (두통 따위를) 잠을 자서 낫게 하다
- sleep on something ~을 밤새 고심하다
- sleep over ~을 빠뜨리고 못보다, 외박하다
- sleep together 이성과 자다, 동침하다
- sleep with 이성과 동침하다
日本語 (Japanese)
v. - 眠る, 永眠する, 泊まる, 宿泊設備がある, 活動しない, 性交する, 異性と寝る
n. - 睡眠, 永眠, 静止, しびれ
idioms:
- get off to sleep 寝つく
- get to sleep 寝つく
- go to sleep 眠る, 寝入る, しびれる
- put to sleep 眠らせる, 麻酔をかける
- sleep around いろいろな相手と寝る
- sleep like a log 熟睡する
- sleep of the just 安眠
- sleep off 眠って治す, 眠って忘れる
- sleep on something 一晩寝て考える
- sleep over 見落とす, 外泊する
- sleep rough 野宿する
- sleep tight ぐっすり眠る
- sleep together 一緒に寝る
- sleep with 異性と寝る
العربيه (Arabic)
(الاسم) هجوع, رقاد, نوم (فعل) يضاجع, يهجع, يرقد, ينام
עברית (Hebrew)
n. - שינה, תרדמה
v. intr. - ישן, נרדם, מת
v. tr. - הלין, סיפק מקומות לינה
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Britannica Concise Encyclopedia
Britannica Concise Encyclopedia. © 1994-2012 Encyclopædia Britannica, Inc. All rights reserved. Read more
Oxford Food & Fitness Dictionary
Food and Fitness: A Dictionary of Diet and Exercise. Copyright © 1997, 2003 by Oxford University Press. All rights reserved.
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Oxford Companion to the Body
The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved.
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Roget's Thesaurus
Roget's II: The New Thesaurus, Third Edition by the Editors of the American Heritage® Dictionary Copyright © 1995 byHoughton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
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American Heritage Dictionary of Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Company. All rights reserved.
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Gale Encyclopedia of Children's Health
© 2006 by The Gale Group, Inc. All rights reserved.
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Oxford Dictionary of Sports Science & Medicine
The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.
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Columbia Encyclopedia
The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2012, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/.
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Oxford Companion to the Mind
The Oxford Companion to the Mind. Second Edition. Copyright © Oxford University Press, 2004. All rights reserved.
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Word Tutor
Copyright © 2004-present by eSpindle Learning, a 501(c) nonprofit organization. All rights reserved.
eSpindle provides personalized spelling and vocabulary tutoring online; sign up free. Read more
eSpindle provides personalized spelling and vocabulary tutoring online; sign up free. Read more
The Dream Encyclopedia
The Dreams Encyclopedia. 1995 ©Visible Ink Press (VisibleInkPress.com). All rights reserved.
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Oxford Dictionary of Modern Slang
Oxford University Press. © 1997, 2008, 2010
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Saunders Veterinary Dictionary
Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.
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Mosby's Dental Dictionary
Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.
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Random House Word Menu
© 2010 Write Brothers Inc. Word Menu is a registered trademark of the Estate of Stephen Glazier.
Write Brothers Inc.
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Bradford's Crossword Solver's Dictionary
Collins Bradford's Crossword Solver's Dictionary © Anne Bradford, 1986, 1993, 1997, 2000, 2003, 2005, 2008
HarperCollins Publishers
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Wikipedia on Answers.com
This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Sleep.
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