Sex- and phenotype-specific prognostic implications of body mass index in acute heart failure

Introduction: This study aimed to determine whether the prognostic implications of body mass index (BMI) differ according to heart failure (HF) phenotype and sex. Methods: From the Korean HF III registry (n = 7351), we analyzed 5271 patients hospitalized for acute heart failure (AHF) with available data. BMI was categorized as low (<18.5 kg/m²), normal (18.5–24.9), or high (≥25.0) using cut-off values consistent with Asia-Pacific criteria. The primary outcome was a composite of 2-year all-cause mortality or heart transplantation. Kaplan–Meier analyses and multivariable Cox proportional hazards models, including interaction terms for BMI, sex, and HF phenotype, were performed. Results: In HF with reduced ejection fraction (HFrEF), lower BMI was consistently associated with worse outcomes in both men and women. In contrast, in HF with preserved ejection fraction (HFpEF), BMI was prognostic in women but not in men: survival differed by BMI category in Kaplan–Meier analyses for all subgroups except men with HFpEF. In multivariable analyses, higher BMI was independently associated with lower risk in women with HFrEF [hazard ratio (HR) 0.66, 95% confidence interval (CI) 0.45–0.96, P = .032], whereas lower BMI in women with HFpEF showed a borderline association with higher risk (HR 1.56, 95% CI 0.99–2.47, P = .057). Conclusion: The prognostic implications of BMI in AHF differ according to HF phenotype and sex. Lower BMI is a consistent adverse marker in HFrEF in both sexes and shows a borderline adverse association in women with HFpEF, whereas BMI is not prognostic in men with HFpEF. These findings highlight the importance of sex- and phenotype-specific interpretation of BMI in risk assessment.