The case-crossover design: a method for studying transient effects on the risk of acute events.
A case-control design involving only cases may be used when brief exposure causes a transient change in risk of a rare acute-onset disease. The design resembles a retrospective nonrandomized crossover study but differs in having only a sample of the base population-time. The average incidence rate ratio for a hypothesized effect period following the exposure is estimable using the Mantel-Haenszel estimator. The duration of the effect period is assumed to be that which maximizes the rate ratio estimate. Self-matching of cases eliminates the threat of control-selection bias and increases efficiency. Pilot data from a study of myocardial infarction onset illustrate the control of within-individual confounding due to temporal association of exposures.
Maclure
M
M
Department of Epidemiology, Harvard School of Public Health, Boston, MA 02115.
D015982:Bias; D016022:Case-Control Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D012107:Research Design; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors