Sex-Based Differences in Early Mortality after Myocardial Infarction

BACKGROUND: There is conflicting information about whether short-term mortality after myocardial infarction is higher among women than among men after adjustment for age and other prognostic factors. We hypothesized that younger, but not older, women have higher mortality rates during hospitalization than their male peers. METHODS: We analyzed data on 384,878 patients (155,565 women and 229,313 men) who were 30 to 89 years of age and who had been enrolled in the National Registry of Myocardial Infarction 2 between June 1994 and January 1998. Patients who had been transferred from or to other hospitals were excluded. RESULTS: The overall mortality rate during hospitalization was 16.7 percent among the women and 11.5 percent among the men. Sex-based differences in the rates varied according to age. Among patients less than 50 years of age, the mortality rate for the women was more than twice that for the men. The difference in the rates decreased with increasing age and was no longer significant after the age of 74 (P< 0.001 for the interaction between sex and age). Logistic-regression analysis showed that the odds of death were 11.1 percent greater for women than for men with every five-year decrease in age (95 percent confidence interval, 10.1 to 12.1 percent). Differences in medical history, the clinical severity of the infarction, and early management accounted for only about one third of the difference in the risk. After adjustment for these factors, women still had a higher risk of death for every five years of decreasing age (increase in the odds of death, 7.0 percent; 95 percent confidence interval, 5.9 to 8.1 percent). CONCLUSIONS: After myocardial infarction, younger women, but not older women, have higher rates of death during hospitalization than men of the same age. The younger the age of the patients, the higher the risk of death among women relative to men. Younger women with myocardial infarction represent a high-risk group deserving of special study.