The Confounded Relation of Coffee Drinking to Coronary Artery Disease

After decades of conflicting studies, the relation of coffee drinking to coronary artery disease (CAD) risk remains unresolved. Using Cox proportional-hazards models with 5 covariates, 127,212 subjects who supplied baseline data at voluntary health examinations from 1978 to 1985 were studied. Subsequently, 8,357 subjects were hospitalized for CAD. Coffee drinking was unrelated to CAD risk in 58,888 never smokers, but in ex-smokers and current baseline smokers, daily coffee intake was associated with higher CAD risk. This disparity was generally consistent in stratified subgroups. In conclusion, this relation of coffee consumption to increased CAD risk only in smokers could be explained by incomplete control for smoking, by other traits of smokers, or by an adverse biologic interaction of a coffee ingredient with smoking effect on CAD.