Risk factors for myocardial infarction in young women.

The interim results of a case-control study of myocardial infarction in women below age 55 years conducted in northern Italy since January 1983 are presented, based on 168 cases of acute myocardial infarction and 251 hospital controls. Cigarette smoking was strongly related to myocardial infarction, with risk estimates elevated more than 10-fold for heavy (more than 25 cigarettes per day) smokers. Smoking-related relative risks were of similar magnitude in younger (less than 45 years) and in perimenopausal (45-54 years) women and were largely unaffected by allowance for several potential distorting factors. Other factors independently and strongly related to the risk of myocardial infarction were diabetes, hypertension, and history of coronary heart disease in more than one first-degree relative. Relative risks were also elevated in women who gave birth to their first child earlier (below age 20 years) and in oral contraceptive users. However, these estimates were not significant. The apparent positive associations with clinical history of hyperlipidemia, hypertension in pregnancy, and heavy coffee consumption could be explained largely in terms of confounding, but the protection conveyed by moderate alcohol consumption remained after multivariate analysis. Thus, the interim results of this investigation in a low incidence population confirm the importance of several risk factors previously described in data collected in Northern Europe and the United States. Furthermore, possibly because of the low baseline risk, the proportion of cases attributable to smoking in middle-aged women in this population may be even larger than that previously reported from higher incidence areas.