A prospective study of oral contraceptive use and risk of myocardial infarction among Swedish women.

OBJECTIVE

To determine the risk for incident myocardial infarction (MI) in women exposed to modern formulations of oral contraceptives (OCs).

DESIGN

Population-based, prospective cohort study begun in 1991 with follow-up through 2002 for an average of 11 years.

PATIENT(S): A total of 48,321 Swedish women aged 30-49 randomly selected from the population residing in the Uppsala Health Care Region of Sweden in 1990-91.

MAIN OUTCOME MEASURE(S): Fatal and nonfatal MI ascertained through linkages with nationwide health registries for death, hospitalization, and emigration.

RESULT(S): There were 214 incident cases of MI. Compared with never users, neither former (relative risk, 1.0; 95% confidence interval, 0.7-1.4) nor current (relative risk, 0.7; 95% confidence interval, 0.4-1.4) OC users at study enrollment had an elevated risk of future MI in models adjusted for coronary heart disease risk factors. Risk of MI was not elevated by prolonged use or in subgroups defined by characteristics of the women or types of OC.

CONCLUSION(S): Use of OC was not associated with an increased risk of MI in this prospective study, in which most current users of OC were taking low-dose estrogen and second- or third-generation progestins.