Matched Case-Crossover Design — Time-Matched Self-Controlled Epidemiological Study

The matched case-crossover design is a self-controlled observational study in which each case serves as its own control. A short hazard window immediately before the acute event is compared with one or more matched control windows — selected to have the same day of week, season, or other time-varying covariate — making the design robust to stable individual confounders and calendar-time trends simultaneously.