Body mass index and the risk of all-cause mortality among patients with nonvalvular atrial fibrillation: a multicenter prospective observational study in China

High body mass index (BMI) is associated with increased incident atrial fibrillation (AF) and mortality rate. In patients presenting with nonvalvular AF (NVAF), the prognostic relevance of BMI remains unclear.In this prospective observational study, a total of 1759 patients with NVAF (69.9±12.9 years old, 47.9% male) were divided into three clinical settings according to estimated stroke risks (CHADS2 score ⩽1 (low), =2 (moderate) and ⩾3 (high)). The primary outcome was all-cause mortality, and the secondary outcomes included thromboembolism and major bleeding. Cox-proportional hazard models were used to estimate the association between BMI levels and clinical outcomes.During a mean follow-up of 1 year representing 1974 patient-years at risk, 256 patients died, 142 suffered from thromboembolism and 17 developed major bleeding. Multivariate adjusted Cox analysis indicated that a BMI of 24.0-27.9 kg/m2 was independently associated with improved survival among all patients (hazard ratio (HR) 0.689, 95% confidence interval (CI) 0.512-0.928; P=0.018) and patients at high stroke risk (HR 0.622, 95% CI 0.410-0.943; P=0.024), but not among those at low or moderate stroke risks. No associations were observed between BMI levels and the incidence of thromboembolic events in various clinical settings.A paradoxical BMI-all-cause mortality risk association was observed in Chinese patients with NVAF, and this association was pronounced among patients at high stroke risk rather than in those at low stroke risk.