Oral contraceptive use and risk of myocardial infarction: an Italian case-control study.

Abstract

In this report oral contraceptive impact on incidence for myocardial infarction in Italian women was studied. This study differs from earlier Northern European and North American studies in the pattern of oral conceptive use and disease incidence. This case-control study was conducted over a 10-year period and included women aged 18-54 years. 251 women admitted to coronary care units who were diagnosed with acute myocardial infarction were study candidates. Case controls were 475 women admitted to the same hospitals who were not suffering from acute myocardial infarction. Analysis was based on an a standard unconditional logistic regression from which were derived the odds ratios (OR) and confidence intervals (CI). It was found that 2.8% of the women with acute myocardial infarction were currently using oral contraceptives. Only 1.3% of the case control women were using oral contraceptives. Reviewing past usage showed that 17.1% of the cases had used oral contraception while 9.7% of the controls had been past users. Risk of disease decreased after stopping oral contraceptive usage. Smoking substantially increased the risk for acute myocardial infarction (an increase of 6.1%; 95% CI 3.4-11.0) in women taking oral contraceptives. Smoking alone accounts for approximately 50% of the acute myocardial infarctions in Italian women. Oral contraceptive use in contrast accounts for only 1% of these cases in Italian women.