Myocardial infarction and the use of estrogen and estrogen-progestogen in postmenopausal women.

Objective: To estimate the relative risk for incident acute myocardial infarction in relation to the current use of estrogen and estrogen-progestogen.
Design: Retrospective case-control study.
Setting: Medical centers of a large prepaid health care program, the Kaiser Permanente Medical Care Program (KPMCP), Northern California region.
Participants: All women hospitalized at a KPMCP center for incident acute myocardial infarction during a 3-year period from 1991 to 1994. Controls were matched to case-patients for year of birth and KPMCP facility and were selected at random from among all female members of the KPMCP.
Intervention: An in-person interview that included questions about current and lifetime use of estrogen and estrogen-progestogen; known cardiovascular risk factors; and other medical, sociodemographic and behavioral factors that might affect risk for myocardial infarction.
Main Outcomes Measure: Odds ratios for myocardial infarction associated with use of estrogen and estrogen-progestogen.
Results: The odds ratio for myocardial infarction in current users of estrogen or estrogen-progestogen compared with women who had never used these agents was 0.96 (95% CI, 0.66 to 1.40) after adjustment for confounders. The odds ratio for myocardial infarction in past users of estrogen or estrogen-progestogen was 1.07 (CI, 0.72 to 1.58). Duration of hormone use was unrelated to the odds ratio for myocardial infarction.
Conclusions: This study did not show a statistically significant decrease in the odds ratio for myocardial infarction associated with current use of estrogen or estrogen-progestogen. It neither confirms nor refutes the hypothesis that hormone use prevents myocardial infarction in postmenopausal women.