Patient sex has been shown to differentially affect mortality from unstable angina (UA) and acute myocardial infarction (AMI). However, to our knowledge, no prior population-based studies have examined both cohorts simultaneously to explain this intriguing variation. Hence, we undertook to explore and explain sex differences in 5-year mortality after UA and AMI.
We used an administrative database of 22 967 patients with AMI and 8441 patients with UA discharged from acute care hospitals in Alberta between April 1, 1993, and March 31, 2000.
Women were older with more baseline comorbidities, more frequently had a diagnosis of UA, and had 30% lower relative odds of undergoing revascularization than men. Kaplan-Meier estimates of 5-year mortality were similar between sexes after UA (women vs men, 21.6% vs 19.5%; P = .09) but markedly higher for women after AMI (38.5% vs 26.6%, P<.001). After adjustment for baseline characteristics and revascularization, the hazard ratios (95% confidence intervals) for women vs men were 0.81 (0.72-0.92) after UA and 0.99 (0.93-1.05) after AMI. Only women younger than 65 years were at a significantly higher risk after AMI. The reasons for this difference in sex-related outcomes between UA and AMI may relate to greater disparities in the AMI cohort with respect to age, comorbidities, neighborhood incomes, and referrals to cardiovascular specialists.
Relative to UA, AMI has a more serious impact on women than men, such that women have a survival advantage when afflicted with UA but lose that advantage with AMI. Additional investigation into the causes, treatment, and policy implications of the age-sex interaction is warranted.