In a cohort study, a group of individuals exposed to a putative risk factor and a group who are unexposed to the risk factor are followed over time (often years) to determine the occurrence of disease . The incidence of disease in the exposed group is compared with the incidence of disease in the unexposed group.
What is the exposure being studied?
The exposure refers to any characteristic that may explain or predict the presence of a study outcome . The outcome refers to the characteristic that is being predicted.
Are cohort studies based on exposure?
Cohort studies can be prospective or retrospective (Figure 2). ... In other words, a cohort of subjects selected based on exposure status is chosen at the present time , and outcome data (i.e. disease status, event status), which was measured in the past, are reconstructed for analysis.
What is an exposure status?
Exposure status is measured to assess the presence or level of exposure for each individual for the period of time prior to the onset of the disease or condition under investigation when the exposure would have acted as a causal factor.
How do you measure outcomes in a cohort study?
Thus, in the above charac- terization of the cohort study, the principal measures of outcome occurrence are incidence (incidence den- sity, cumulative incidence) of states of health or dis- ease and/or overall and cause-specific mortality .
What are the types of cohort studies?
There are two types of cohort studies: Prospective and Retrospective . The two groups of cohorts (exposed and un-exposed) are followed prospectively over time to track the development of new disease.
What is the aim of cohort study?
A cohort study identifies a group of people and follows them over a period of time. The aim is to look at how a group of people are exposed to different risk factors which may affect their lives . Cohort studies can look at many different aspects of people’s lives, including their health and/or social factors.
What are the 3 major types of epidemiologic studies?
EPIDEMIOLOGIC STUDY DESIGNS
Three major types of epidemiologic studies are cohort, case-control, and cross-sectional studies (study designs are discussed in more detail in IOM, 2000). A cohort, or longitudinal, study follows a defined group over time.
How do we measure exposure?
The most common measurement utilized is the concentration of a given agent . Area monitors are used to estimate exposure to individuals living within a certain proximity and personal monitors can be used to measure individual-specific exposure.
What are the characteristics of a cohort study?
The characteristic feature of a cohort study is that the investigator identifies subjects at a point in time when they do not have the outcome of interest and compares the incidence of the outcome of interest among groups of exposed and unexposed (or less exposed) subjects.
What are examples of exposure?
When someone introduces you to theatre , this is an example of a situation where you receive exposure to theatre. When you are outside for too long in the winter and get sick, this is an example of exposure. The condition of being exposed, especially to severe weather or other forces of nature.
What is the difference between cohort and case-control?
Whereas the cohort study is concerned with frequency of disease in exposed and non-exposed individuals, the case-control study is concerned with the frequency and amount of exposure in subjects with a specific disease (cases) and people without the disease (controls).
What is the exposure in a case-control study?
A case-control study is designed to help determine if an exposure is associated with an outcome (i.e., disease or condition of interest). ... When the subjects are enrolled in their respective groups, the outcome of each subject is already known by the investigator.
What is an example of a cohort?
The term “cohort” refers to a group of people who have been included in a study by an event that is based on the definition decided by the researcher. For example, a cohort of people born in Mumbai in the year 1980. This will be called a “birth cohort.” Another example of the cohort will be people who smoke .
What is an example of a cohort effect?
An example of a cohort effect could be seen in an experiment in which participants use a computer to perform a cognitive task . The results might show that participants in their 20s did vastly better on the cognitive test that participants in their 60s.
Is a cohort study quantitative or qualitative?
Experiments done in a laboratory will almost certainly be quantitative . In a health care context, randomised controlled trials are quantitative in nature, as are case-control and cohort studies. Surveys (questionnaires) are usually quantitative .
