Oral contraceptive use and the risk of myocardial infarction.

The relation of oral contraceptive use to the risk of myocardial infarction was assessed in a hospital-based case-control study of women aged 25-64 years conducted from 1985 to 1988 in New England; 910 women with first myocardial infarctions were compared with 1,760 control women. Oral contraceptive use, after discontinuation, was not associated with an increased risk of myocardial infarction, whether use had ceased in the distant past or more recently. The overall relative risk estimate for women who had used oral contraceptives in the past for at least 5 years compared with nonusers was 1.1 (95% confidence interval 0.8-1.5) after allowance for confounding factors. Past use was not associated with risk in any age group, in subgroups of women with predisposing factors, or in women at low risk because of the absence of predisposing factors. The results suggest that long-term oral contraceptive use, after discontinuation, does not influence the risk of myocardial infarction. There were few current users and the results for current use were inconclusive: for premenopausal women who had used oral contraceptives in the previous month relative to those who had not, the age-adjusted relative risk estimate was 1.1 (95% confidence interval 0.4-3.1).