A researcher investigates whether heavy physical exertion can trigger acute myocardial infarction. For each patient admitted with MI, she asks about exertion during the 2 hours before symptom onset and compares this with exertion during matched 2-hour control periods from the same patient's previous days. Each subject serves as his own control. This design is called:

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

Explanation

The case-crossover design is built for transient exposures that briefly raise the risk of an acute event. Each case acts as his own control, comparing exposure immediately before the event with exposure during earlier comparable periods, which automatically controls fixed confounders like genotype and chronic habits. B cross-over trial involves intervention allocation, not observational exposure assessment.

Reference: Modern Epidemiology (Rothman, Greenland, Lash), 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.