SMOKING AND THE INCIDENCE OF CORONARY HEART-DISEASE IN AN AUSTRALIAN POPULATION

Objective: To estimate the impact of smoking on the incidence of coronary heart disease in Australia. Data collected for the WHO MONICA Project were used. Design: Combined data from a community-based register of all suspected coronary events and a survey of risk factor prevalence in a random sample of the same population. Setting and participants: All residents of the Hunter Region of New South Wales aged 35-69 years who had a first acute myocardial infarction or fatal heart attack (without a history of coronary heart disease) between 1 January 1986 and 31 December 1990. Main outcome measures: Acute myocardial infarction or coronary death, as defined by the WHO MONICA Project. Results: Men who are current smokers are 2.9 times (95% Cl, 2.7-3.1) more likely than non-smokers to have a first myocardial infarction or fatal heart attack, and for women the equivalent figure is 3.5 times (95% CI, 3.2-3.8), after adjusting for age. Current male smokers with a history of hypertension are 4.5 times more likely to have a coronary event (7.9 times in women) than are non-smokers without a history of hypertension. The age-adjusted excess rate was 566 per 100 000 per year in men and 373 per 100 000 per year in women. Smoking is a stronger predictor of coronary heart disease incidence than a history of hypertension (relative risk [RR] = 1.6 for men and 1.9 for women) or a known history of hypercholesterolaemia (RR not significantly different from 1). Conclusions: Cigarette smoking plays a more important role in the causation of a first myocardial infarction or fatal heart attack and appears to have more influence on the incidence of coronary heart disease in Australia than hypertension.