A cohort study identifies groups by exposure status and follows them over time, measuring disease occurrence in each. Prospective cohorts follow subjects forward while retrospective cohorts reconstruct exposure and outcomes from existing records.
It permits direct calculation of incidence and relative risk.
Alternative Names:
Prospective Study, Follow-Up Study
Why it Matters?
Cohort design is considered stronger evidence than case-control because exposure is determined before disease occurs, which eliminates recall bias. The limitations are cost, duration, and statistical power for rare outcomes, since following a cohort long enough to observe rare cancers requires enormous sample sizes. Loss to follow-up is the other methodological vulnerability worth examining.
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Frequently asked questions
Why is cohort design considered stronger?
What are the limitations?
