Participants in a cohort study are grouped according to their
exposure status. In many cohort studies two groups of people
are compared, namely an “exposed group†and an “unexposed
groupâ€. For example, comparisons might be made between
children who have received the MMR vaccine (exposed group)
and children who haven‟t received the MMR vaccine
(unexposed group). Or comparisons might be made between
smokers (exposed group) and non-smokers (unexposed group).
However, you will also encounter studies where more than two
groups will be compared and where researchers divide study
participants into a number of groups with different levels of
exposure. For example, in a cohort study investigating the
association between caffeine consumption during pregnancy and
miscarriage, women were categorised into three groups:
a) women who consumed ≥ 200mg caffeine/day, b) women
who consumed <200mg caffeine/day, c) women who consumed
0mg caffeine/day.
In a cohort study, the groups being compared will be „followed up‟ over a period of time and the incidence of the outcome of
interest will be compared between the groups e.g. researchers
might compare the incidence of autism between groups of
children who have and haven‟t received the MMR vaccine; or
they might compare the incidence of lung cancer between
smokers and non-smokers; or they might compare the incidence
of miscarriage between women with different levels of daily
caffeine consumption etc.6
Two incidence measures can be used to compare the groups:
a) the risk (cumulative incidence) of the outcome of interest can
be calculated in the „exposed‟ and „unexposed‟ groups. The
relative risk can then be calculated by dividing the risk of the
outcome in the exposed group by the risk of the outcome in the
unexposed group.
b) The „incidence rate‟ of the outcome of interest can be
calculated in the „exposed‟ and „unexposed‟ groups (e.g. we can
compare the incidence rate of lung cancer in smokers and nonsmokers). The “incidence rate ratio†can then be calculated by
dividing the incidence rate of the outcome in the exposed group
by the incidence rate of the outcome in the unexposed group.
(you will learn about “incidence rate ratios†during your lectures
next year).
To carry out a cohort study, first identify a group of individuals without the outcome of interest (e.g., a specific disease). Then, determine their exposure status (e.g., exposure to a specific risk factor). Follow these individuals over time and collect data on new occurrences of the outcome. Finally, compare the incidence of the outcome between exposed and unexposed groups to assess the association between the exposure and the outcome.
The cohort in this study was formed based on the shared characteristic of being born in 1976. This characteristic allows the scientist to follow this group of individuals over time to observe their health outcomes.
A cohort study is a type of observational research where a group of individuals with a common characteristic or experience are followed over time to study how certain factors may influence outcomes such as disease development. This design allows researchers to measure the incidence of outcomes in relation to exposures, helping to establish causal relationships and identify risk factors.
A cohort study is a type of research design where a group of individuals sharing a common characteristic are followed over a period of time to observe outcomes. By comparing outcomes between the exposed and unexposed groups, researchers can assess the impact of the particular characteristic on the outcomes of interest. This study design is frequently used in epidemiology to investigate the causes of diseases.
An example of a cohort study is tracking a group of individuals who are exposed to a particular risk factor (e.g., smoking) and comparing their health outcomes over time with a similar group that is not exposed. This type of study allows researchers to assess the impact of the risk factor on the development of certain diseases or conditions.
One disadvantage of a cohort study is the potential for loss to follow-up, which can introduce bias if the characteristics of those lost differ systematically from those who remain. Additionally, cohort studies can be time-consuming, resource-intensive, and require a long follow-up period to observe outcomes, making them impractical for some research questions. Bias in exposure assessment or outcome measurement can also affect the validity of results in cohort studies.
it is prospective cohort study
A panel study uses a representative sample, whereas a cohort study uses a sample with predetermined common characteristics.
A longitudinal cohort study involves studying a specific group of people over an extended period of time.
What is major problem resulting from the lack of randomization in a cohort study
A cohort study is considered primary literature because it involves original research conducted by the authors.
Quantitative
Occupation
Age.
behavior
The three main types of longitudinal studies are cohort studies, panel studies, and trend studies. Cohort studies follow a specific group of individuals over time, panel studies revisit the same group of individuals at multiple points, and trend studies analyze data collected from different samples at various time points.
Age
What is my age cohort