Attributable risks for nonfatal myocardial infarction in Italy

Background. The proportions of nonfatal acute myocardial infarctions (AMI) in Italy attributable to cigarette smoking, body mass, serum cholesterol level, hypertension, diabetes, and family history of AMI (attributable risks, AR) were estimated using data from a case-control study on 614 incident cases of AMI before age 75 with no history of ischemic heart disease and 792 control subjects admitted to the same hospitals where cases were identified for acute, nonneoplastic, cardio- or cerebrovascular conditions not known or suspected to be related to cigarette smoking. Methods. The study was conducted between September 1988 and June 1989 within the framework of the GISSI-2 clinical trial. We assumed a multiplicative model and thus the risk attributable to several factors combined is not the sum of those attributable to the single factors. Results. Overall the AR of smoking was 49%, and for cholesterol, body mass, family history of AMI, hypertension, and diabetes the AR were 49, 16, 14, 13, and 6%, respectively. Together these factors explained 86% of AMI cases. Though differences emerged for each single factor, the proportion of AMI explained by the six factors together was approximately the same for both sexes, while these factors accounted for 97% of AMI cases before age 50 (and smoking alone for 70%) and for 80% after age 50. Conclusions. This study confirms that interventions on well-defined risk factors could, in principle, lead to the avoidance of the great majority of myocardial infarctions in this population (i.e., about 80% before age 75 and about 95% before age 50).