Outcomes in Patients With Atrial Fibrillation Stratified by Body Mass Index and Heart Failure Status

Background: An obesity-survival benefit, called the “obesity paradox,” has been variably reported in patients with heart failure (HF) and those with atrial fibrillation (AF), but inconsistencies have been observed. Objectives: The purpose of this study was to assess how the interaction between body mass index (BMI) and HF status impacts AF-related outcomes. Methods: Patients hospitalized for AF in the Get With The Guidelines-Atrial Fibrillation registry from 2013 to 2021 and linked to Medicare claims were included. Adjusted Cox proportional hazards models were used to assess the association between BMI and outcomes, stratified by HF status (no HF, HF with preserved ejection fraction, HF with mid-range ejection fraction, and HF with reduced ejection fraction). The outcomes were mortality, cardiovascular rehospitalization, thromboembolism, and myocardial infarction within 1 year. Results: In total, 21,850 patients (mean age 77 years, 42.3% male) were included: 29.5% underweight/normal (BMI<25 kg/m²), 32.0% overweight (BMI 25-29.9), and 38.5% obese (BMI =30). Increasing BMI was associated with lower mortality in patients without obesity and without HF (HR: 0.94 per 1 kg/m² increase; 95% CI: 0.92 to 0.95), with HF with reduced ejection fraction (HR: 0.96; 0.93-0.99), and with HF with preserved ejection fraction/HF with mid-range ejection fraction (HR: 0.93; 0.92-0.95), while increases in BMI among patients with obesity were not associated with lower mortality (interaction P = 0.013). The risks of cardiovascular rehospitalization, thromboembolism, and myocardial infarction were not significantly different across the HF spectrum between patients with and without obesity (all interaction P > 0.05). Conclusions: Higher BMI was associated with increased survival in patients without obesity, irrespective of HF status, but not in patients with obesity and AF.