First coronary heart disease event rates in relation to major risk factors: Quebec cardiovascular study

The incidence of first coronary heart disease (CHD) events was evaluated prospectively in relation to the baseline measurements of systolic and diastolic blood pressure, serum cholesterol, smoking status and education in a cohort of 4576 Quebec men aged 35 to 64 and free from CHD at entry in 1974. From 1974 to 1986, 603 first CHD events were documented. The most frequent first manifestation was angina (6.7/1000 person-years) followed by nonfatal myocardial infarction (4.7/1000) and CHD death 2.2/1000). There was a positive relationship between the first CHD event and systolic (Z = 4.67) and diastolic (Z = 6.50) blood pressure. This relation was observed for angina, nonfatal myocardial infarction and CHD death. Serum cholesterol was also related to all events (Z = 4.99) but more specifically to angina and nonfatal myocardial infarction. Cigarette smoking was significantly related to first CHD manifestations. This relationship for specific CHD events was observed in men who smoked more than 20 cigarettes per day. Men who discontinued smoking one year before the study had a risk not different from those who never smoked. No relationship was observed between years of schooling and CHD events. Blood pressure, cholesterol and smoking constituted nearly two-thirds of the attributable risk of first CHD events.