A study of triggers for acute myocardial infarction enrolls patients who suffered an MI and compares their physical activity level in the 60 minutes preceding the event with their usual activity level at the same time of day on control days. Each patient serves as his or her own control. Which study design is this?

• A Nested case-control study
• B Cross-over randomized trial
• C Retrospective cohort study
• D Case-crossover study ✓

Explanation

The case-crossover design is used when the exposure is brief, transient and close in time to an abrupt outcome such as MI, injury or asthma attack. Each subject acts as his or her own control, comparing hazard periods with control periods, which automatically controls for fixed individual characteristics. A cross-over randomized trial involves deliberate intervention allocation, not observation after a spontaneous event.

Reference: Gordis Epidemiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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