What is exposure in cohort study?
What is exposure in cohort study?
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. In a retrospective cohort study both the exposure and outcome have already occurred at the outset of the study.
Can cohort study multiple exposures?
A major advantage of cohort studies in general is the possibility to study multiple exposures and multiple outcomes in one cohort. Even rare exposures can be studied, for the index group can be selected on this exposure.
Can a nested case-control study be prospective?
As with cohort studies, case-control studies can be prospective or retrospective.
What is an exposure in a study?
The exposure and outcome of a study depend on the proposed study question. 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.
What is exposure measure?
Definition. Exposure assessment is the process of estimating or measuring the magnitude, frequency and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment.
Why do a nested case control study?
Thus the nested case–control study is more efficient than the full cohort design. The nested case–control study can be analyzed using methods for missing covariates. The NCC design is often used when the exposure of interest is difficult or expensive to obtain and when the outcome is rare.
How many groups are in a cohort study?
two groups
Such studies typically follow two groups of patients for a period of time and compare an endpoint or outcome measure between the two groups.
Why We Use nested case-control study?
How does a nested case-control work?
In the nested case-control study, cases of a disease that occur in a defined cohort are identified and, for each, a specified number of matched controls is selected from among those in the cohort who have not developed the disease by the time of disease occurrence in the case.
What is a nested case-control study?
This is referred to as a case-control study “nested” within a cohort study. Rothman states that one should look upon all case-control studies as being “nested” within a cohort. In other words the cohort represents the source population that gave rise to the cases.
What is the relationship between exposure and outcome in a cohort?
Since at the time of entry into the cohort study, the individuals do not have outcome, the temporality between exposure and outcome is well defined in a cohort design. If the exposure is rare, then a cohort design is an efficient method to study the relation between exposure and outcomes.
What is the difference between a cohort study and case-control study?
Obviously, this is a much more efficient design. It is important to note that, unlike cohort studies, case-control studies do not follow subjects through time. Cases are enrolled at the time they develop disease and controls are enrolled at the same time.
What is a cohort design in research?
In a cohort study, participants who do not have the outcome at baseline are followed over time to estimate the incidence of the outcome. In this type of design, the temporality between the exposure and outcome is well defined. The studies may be prospective, retrospective, or a mixture of both.
