Myocardial Infarction and Oral Contraceptive Use in Women under 50

Objectives

  • To determine whether current or past use of oral contraceptives is associated with an increased risk of nonfatal myocardial infarction.
  • To identify subgroups of women at higher risk for myocardial infarction, given oral contraceptive exposure.
  • To determine the separate and combined effects of oral contraceptive use and other risk factors.

Methods

Cases of acute first myocardial infarction in women below the age of 50 years were ascertained by weekly telephone calls to 155 collaborating hospitals located in Eastern Massachusetts, Southern Connecticut, Long Island, and metropolitan Philadelphia. Nurse-interviewers were stationed in each geographic area. Patients were interviewed in hospital prior to discharge. Suitable control subjects in the same or nearby hospitals were also interviewed. In the fourth year of the study, 300 patients with myocardial infarction (one-half of the cases) and 600 controls, drawn from the same geographic areas as the 300 cases, were studied a second time, during which blood samples were drawn and data concerning personality were obtained. Plasma cholesterol, high-density lipoprotein levels, triglycerides and ABO blood groups were determined.

Results

The risk of myocardial infarction was greatly increased among current users of oral contraceptives who smoked ≥25 cigarettes per day. High levels of total cholesterol and low levels of high density lipoprotein cholesterol were associated with increased risk of myocardial infarction.