Smoking and acute myocardial infarction among women and men : a case- control study in Italy

Background. A few studies have compared the smoking-related risk of acute myocardial infarction (AMI) among women and men from the same population. A clear assessment of AMI risk among female smokers is now of major public health importance, given the large number of women who smoke. Methods. The study is based on two case-control studies, conducted in Italy between 1983 and 1992, including 429 women and 801 men with AMI, and 863 female and 976 male controls, in hospital for acute conditions, unrelated to tobacco consumption, other than cardio or cerebrovascular and neoplastic. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were estimated by unconditional multiple logistic regression, including terms for study center, age, education, and other major risk factors of cardiovascular disease. Results. Compared with non-smokers, the OR was 4.1 (95% CI 2.3-5.7) for female and 3.3 (95% CI 2.4-4.6) for male current smokers. The OR for smokers of <15 cigarettes per day was 2.4 for women and 2.1 for men; the sex difference was more evident for smokers of 15 to 24 cigarettes per day (OR 5.6 for women and 3.2 for men) and of ≥ 25 cigarettes per day (OR 9.8 for women and 5.4 for men). The ORs in increasing duration categories were 3.6, 4.2, and 25.0 for women and 3.1, 3.9, and 3.2 for men. There was an inverse relation between the smoking-related risk of AMI and age among men, but no clear pattern with age was observed among women. Conclusions. Our study confirms that the relative risk of AMI is higher among female than among male smokers, and the difference is greater for heavy and long-term smokers.