To study the association between oral contraceptive use and stroke, researchers identify all new stroke cases occurring over five years within a pre-existing cohort of 50,000 women enrolled in a hormonal health registry, and select a random sample of non-stroke women from the same cohort as comparators. This design is best described as:

• A Case-cohort study
• B Case-crossover study
• C Retrospective cohort study
• D Nested case-control study ✓

Explanation

A nested case-control study is conducted entirely within an identified cohort: incident cases arising during follow-up are compared with a sampled subset of controls drawn from those still at risk at the time each case occurs. This preserves the advantages of the cohort while reducing cost. A retrospective cohort would analyze the entire cohort rather than samples, and a case-cohort study samples the comparison group from the baseline cohort regardless of subsequent case status, which differs from risk-set sampling.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.