Related Experiment Videos
Low-dose oral contraceptive use and the risk of myocardial infarction
L Rosenberg1, J R Palmer, R S Rao
1Slone Epidemiology Unit, Boston University School of Medicine, 1371 Beacon St, Brookline, MA 02446, USA. lrosenberg@slone.bu.edu
Background:
Studies of oral contraceptives (OCs) containing 50 microg or more of estrogen suggest an increased risk of myocardial infarction (MI) among current users, particularly if they smoke heavily.
Objective:
To assess whether use of the newer lower-dose OCs increases the risk of MI.
Methods:
A case-control study was conducted from January 1985 through March 1999 in 75 hospitals in the greater-Boston and greater-Philadelphia areas. Data on OC use and MI risk factors were obtained by interview from 627 women with a nonfatal first MI (cases) and 2947 female hospital controls younger than 45 years.
Results:
The overall odds ratio (OR) for current OC use relative to never used was 1.3 (95% confidence interval [CI], 0.8-2. 2). The OR was elevated, 2.5 (95% CI, 0.9-7.5), among heavy smokers (>/=25 cigarettes per day) but close to 1.0 among lighter smokers (OR = 0.8) and nonsmokers (OR = 1.3). For current OC use together with heavy smoking relative to nonuse and nonsmoking, the OR was 32 (95 % CI, 12-81), considerably greater than that for heavy smoking alone, 12 (95% CI, 8.6-16). The ORs did not vary according to the type of formulation or the dose of estrogen; there were too few users to assess the new 20-microg preparations. Past OC use was unrelated to risk.
Conclusion:
Current use of low-dose OCs in the United States is unrelated to an increased risk of MI among nonsmokers and light smokers, but users who smoke heavily may be at greatly increased risk.