The contribution of smoking to socioeconomic differentials in mortality: Results from the Melbourne Collaborative Cohort Study, Australia

Objective: To assess the contribution of smoking to the inverse association of mortality with years of formal education in men in Australia. Design: Data were obtained from a prospective cohort study that included 17 049 men in Melbourne recruited from 1990 to 1994, most of whom were aged between 40 and 69 years at baseline. The outcome measured was all-cause mortality. The contribution of smoking to socioeconomic status differentials was estimated by including smoking as a variable in a Cox's proportional hazards model that also included education and other potential confounding variables. Results: In men, the association between education and mortality was attenuated after adjustment for smoking, and the aetiological fraction for low levels of education was reduced from 10.5% to 10.6%. Conclusions: In men, smoking contributes substantially to socioeconomic differentials in mortality. Effective policies and interventions that target smoking among socially disadvantaged groups may substantially reduce socioeconomic differentials in health.