To test whether brief mobile phone use immediately before driving increases the risk of a road traffic crash, investigators compare each injured driver's phone activity in the 30 minutes preceding the crash with his own phone activity during matched control periods the previous week. This design is called:
- A Case-crossover study ✓
- B Crossover randomized trial
- C Case-control study
- D Interrupted time series
Explanation
The case-crossover design is used for transient exposures with immediate effects on acute outcomes. Each subject serves as his own control, with exposure just before the event compared against exposure during earlier control windows, which automatically controls for stable personal characteristics such as personality, driving skill and chronic habits. C conventional case-control uses separate control persons, a crossover trial is an experimental design with planned treatment sequences, and interrupted time series analyses population level trends around an intervention rather than individual trigger exposures.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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