Divergent associations of body mass index with short- and long-term prognosis in heart failure with reduced and mildly reduced ejection fraction: A retrospective cohort study.

BACKGROUND: Obesity is closely related to cardiovascular outcomes. However, the prognostic value of body mass index (BMI) in patients with heart failure with mildly reduced ejection fraction (HFmrEF) and heart failure with reduced ejection fraction (HFrEF) remains unclear. OBJECTIVE: To investigate the association of BMI with 1-year heart failure readmission and 5-year all-cause mortality in patients with HFmrEF and HFrEF. METHODS: We consecutively enrolled patients hospitalized for HFrEF and HFmrEF between January 2018 and December 2020. Participants were categorized into underweight, normal weight, overweight, and obese groups by baseline BMI. Associations of BMI with readmission and mortality were analyzed using the Fine-Gray test, Cox proportional hazards model, and restricted cubic splines. RESULTS: Among 656 included patients, the readmission and mortality risk varied significantly across BMI groups (both Gray's test and log-rank P < 0.001). Compared to normal weight group, both overweight (sHR 1.60, 95% CI [1.24, 2.07]) and obese (sHR 1.83, 95% CI [1.39, 2.39]) groups showed significantly increased 1-year heart failure readmission risk. For 5-year all-cause mortality, the underweight (HR 2.30, 95% CI [1.62, 3.26]) and obese (HR 2.03, 95% CI [1.42, 2.91]) groups exhibited significantly higher risk. No significant interaction between BMI and heart failure phenotype was observed. Restricted cubic splines revealed a U-shaped relationship of BMI with mortality risk, but provided weak evidence on risk of readmission. CONCLUSION: BMI exerts divergent time- and outcome-dependent effects in HFrEF and HFmrEF. Obesity may be associated with short-term readmission risk, while underweight may be related to cachexia-associated long-term mortality.