Sex-specific associations between body mass index and short-term outcomes in patients with acute myocardial infarction

Background Body mass index (BMI) has been associated with prognosis in patients with acute myocardial infarction (AMI), yet potential sex-specific differences remain insufficiently characterized. We aimed to evaluate sex-specific associations between BMI and short-term mortality in AMI patients. Methods This multicenter, real-world cohort study enrolled consecutive AMI patients from 82 hospitals between 2010 and 2024, including 67,183 men and 34,110 women. BMI was categorized according to Chinese criteria as underweight (<18.5 kg/m²), normal weight (18.5–23.9 kg/m²), overweight (24.0–27.9 kg/m²), and obese (≥28.0 kg/m²). Baseline characteristics, comorbidities, in-hospital treatments, and outcomes were compared across BMI categories stratified by sex. Sex-stratified multivariable Cox proportional hazards models were used to estimate 3-month all-cause mortality. Results Patients in the Underweight group were notably older. Obese patients had the highest prevalence of cardiovascular risk factors, including Diabetes Mellitus (Male: 17.7% vs. 24.7% vs. 28.6% vs. 31.1%, p<0.001; Female: 16.4% vs. 29.6% vs. 35.4% vs. 37.1%, p<0.001) and Hypertension (Male: 42.5% vs. 45.3% vs. 49.3% vs. 52.6%, p<0.001; Female: 39.6% vs. 51.1% vs. 56.0% vs. 59.4%, p<0.001). Regarding in-hospital management, Obese patients more frequently received revascularization (Male: 46.2% vs. 60.7% vs. 63.7% vs. 65.0%, p<0.001; Female: 29.6% vs. 44.9% vs. 50.1% vs. 50.1%, p<0.001) and guideline-directed medical therapy (Figure 1). After multivariable adjustment, obesity was independently associated with increased 3-month mortality in men (aHR: 1.13, 95% CI: 1.01–1.26; p = 0.039), whereas overweight and underweight were not significantly associated with mortality. In women, overweight was associated with reduced 3-month mortality (aHR: 0.89, 95% CI: 0.81–0.97; p = 0.009), while obesity showed no significant association (p for interaction=0.004) (Figure 2). Conclusions The prognostic impact of BMI in AMI differs significantly by sex. Obesity confers increased short-term mortality risk in men, whereas overweight is associated with improved survival in women. These findings underscore the importance of incorporating sex–BMI interaction into risk stratification strategies for AMI patients.