Historic cohort study

Historic Cohort Study is a type of observational study that involves the identification of two groups (cohorts) of individuals, one which received the exposure of interest, and one which did not, and following these cohorts forward for the outcome of interest.

Overview

In a Historic Cohort Study, the investigator identifies the original cohort at some point in the past, and determines their exposure at that time. The investigator then traces these individuals to the present, and determines their current status with respect to the outcome of interest. This type of study design is often used when the exposure of interest is rare, and it would be inefficient or infeasible to wait for sufficient numbers of individuals to develop the exposure in a prospective cohort study.

Advantages and Disadvantages

Advantages:

• Can be conducted when the exposure of interest is rare.
• Can be conducted more quickly than a prospective cohort study, as the outcomes have already occurred.

Disadvantages:

• Potential for bias due to the retrospective nature of the study.
• Difficulty in accurately determining exposure status and outcome status, as this relies on historical records.
• Potential for confounding, as it may be difficult to control for all potential confounding variables.

Examples

An example of a historic cohort study is the British Doctors Study, which was a historic cohort study that investigated the link between smoking and lung cancer. The study identified a cohort of British doctors who were smokers at the start of the study, and a cohort of doctors who were non-smokers. The study then followed these cohorts forward in time, and found that the smokers had a much higher risk of developing lung cancer than the non-smokers.

See Also

• Cohort study
• Observational study
• Prospective cohort study
• Retrospective cohort study

Historic cohort study Resources
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