Background: The female sex is associated with poorer outcomes after myocardial infarction (MI), although current evidence in older patients is limited and mixed. We sought to evaluate sex-based differences in outcome after MI in older patients.

Methods: Consecutive older (≥ 70 years) all-comer patients with out-of-hospital MI admitted to 20 hospitals in Finland between 2005-2014 were studied using national registries (n=40,654, mean age 80 years, 50% women). The outcome of interest was death within one year after MI. Differences between sexes (age, baseline features, medication, comorbidities, revascularization, and treating hospital) were balanced by inverse probability weighting.

Results: Adjusted all-cause case fatality was lower in women than in men at 30 days (16.0% vs. 19.0%, respectively) and at 1 year (27.7% vs. 32.4%, respectively) after MI (hazard ratio: 0.83; confidence interval [CI]: 0.80-0.86; p<0.0001). Excess 1-year case fatality after MI compared to the corresponding general population was 22.1% (CI: 21.4-22.8%) in women and 24.1% (CI: 23.4-24.9%) in men. Women had a lower adjusted hazard of death after MI in subgroups of patients aged 70-79 years and ≥80 years, patients with and without ST elevation MI, revascularized and non-revascularized patients, patients with and without atrial fibrillation, and patients with and without diabetes. The sex difference in case fatality remained similar during the study period.

Conclusions: Older women were found to have a lower hazard of death after an out-of-hospital MI when compared to older men with similar features and treatments. This finding was consistent in several subgroups.