The proportional hazards model: applications in epidemiology

Cox's (1972) Proportioal hazards failure time model, already widely used in the analysis of clinical trials, also provides an elegant formalization of the epidemiologic concept of relative risk. When used to compare the disease experience of a study cohort with that of an external control population, it generalizes the notions of the standardized morbidity ratio (SMR) and the proportional morbidity ratio (PMR). For studies in which matched sets of cases and controls are sampled retrospectively from the population at risk, the model provides a flexible tool for the regression analysis of multiple risk factors.