A researcher wants to study whether heavy physical exertion acts as a trigger for acute myocardial infarction. Each patient serves as his own control, and the exposure window immediately preceding the event is compared with a control window at another time. Which study design is this?
- A Case-crossover study ✓
- B Nested case-control study
- C Case-cohort study
- D Retrospective cohort study
Correct answer: A. Case-crossover study
Explanation
The case-crossover design, described by Maclure, is used for transient exposures that trigger acute events. Each case serves as its own control by comparing exposure frequency just before the event with exposure during a defined earlier period, which automatically controls for fixed individual confounders. B nested case-control study samples controls from within a defined cohort and would not use the patient as his own control.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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