Cigarette smoking and acute myocardial infarction: a case-control study from Argentina

Correspondence to: C La Vecchia Abstract Objective To assess the relationship be tween cigarette smoking and the risk of acute myocardial infarction in Argen tina. Design Hospital-based case-control study conducted between 1984 and 1989 in Buenos Aires. Main outcome measures were multiple logistic regression analysis of relative risk (RR) estimates, and the corresponding 95% confidence intervals (CI), according to smoking status. Al lowance was made for sex, age, education, body mass index, diabetes, hypertension, and family history of coronary heart disease. Setting-A network including 11 coron ary care units from major hospitals in Buenos Aires. Subjects Cases were 1000 patients with acute myocardial infarction. Controls were 1000 patients admitted to the same network of hospitals with a wide spec trum of acute disorders unrelated to smoking or to known or suspected risk factors for myocardial infarction. Results After allowance for major risk factors for myocardial infarction, com pared to lifelong non-smokers, the RRs were 1.6 (95% CI = 1.1 to 2.4) for current smokers of less than 15 cigarettes per day, 2.2 (95% CI = 1.6 to 3.0) for smokers of 15-24, and 5.9 (95% CI = 4.2 to 8.3) for smokers of 25 or more cigarettes per day. The RR was 1.5 (95% CI = 1.1 to 2.0) for ex-smokers who had been abstinent for at least one year. The RR at younger age (30-44 years) was 10.3 (95% CI = 4.3 to 24.9) for heavy smokers (^ 25 cigarettes per day), and declined with advancing age. Conclusions Cigarette smoking is an independent and important risk factor for acute myocardial infarction, and about 40% of cases in this Argentinian population (and over 55% of cases under age 55) are attributable to it. {Tobacco Control 1993; 2: 127-131)