The synergistic effect of smoking and serum cholesterol on coronary heart disease.

Cigarette smoking is a strong predictor of coronary heart disease (CHD), but much of the variance in determining which smokers will, and which will not, suffer from CHD remains unexplained. This review examines evidence of a synergistic interaction effect of smoking and elevated serum cholesterol on CHD morbidity and mortality. Evidence is also presented to support the notion that, in part, serum cholesterol, like smoking, is an index of a behavioral risk factor. Such a synergistic interaction is determined to exist, although improvements in methodology are needed to more clearly identify its magnitude. The review suggests that behavioral treatments aimed at smoking cessation and dietary modification should be focused specifically on the more than 25 million young and middle-aged Americans who smoke and have elevated serum cholesterol. In this way, such treatments may increase their effectiveness in lowering the risk of CHD (benefit) without necessarily increasing their effort (cost).