Cigarette smoking. Its relationship to coronary heart disease and related risk factors in the Western Collaborative Group Study

The association of the incidence of coronary heart disease (CHD) with smoking habits was studied for 4½ years in over 3,000 healthy, employed men, aged 39 to 59 years, at intake into a prospective, epidemiological investigation. The risk of CHD was significantly associated both with current and former cigarette usage. More specifically, this association was found to prevail in men suffering symptomatic and fatal myocardial infarction but not in men sustaining silent myocardial infarction or angina pectoris only and was much stronger in younger than in older age groups. Altered risk of CHD was not found in pipe or cigar smokers. Cigarette habits at intake were associated with differences in serum lipids and other risk variables, but when the latter were controlled statistically, the smoking-CHD associations remained. The cigarette-CHD relationship was studied further in men with and without the coronary-prone behavior pattern (type A). In the younger age decade the increased risk of CHD associated with moderate and heavy cigarette smoking occurred primarily in men with the type A behavior pattern.