Association between body mass index and long-term clinical outcomes in patients with non-valvular atrial fibrillation taking oral anticoagulants

Background and aims The association between body mass index (BMI) and clinical outcomes of patients with non-valvular atrial fibrillation (NVAF) taking oral anticoagulants (OACs) are controversial, and we thus analyzed the large registry data to elucidate them. Methods and results We conducted a historical cohort study at 71 centers in Japan and included outpatients with NVAF taking vitamin K antagonists (VKAs). Physicians in charge could change VKAs to direct OACs based on their judgement during follow-up period. We categorized patients into four BMI groups (kg/m(2)): underweight (BMI < 18.5), normal weight (18.5 <= BMI < 25), overweight (25 <= BMI < 30), and obese (30 <= BMI). The effects of each BMI group relative to the normal weight group on clinical outcomes consisting of all-cause death, ischemic events, and bleeding events were estimated using Cox proportional hazard models adjusting for potential confounders. We also constructed restricted cubic spline regression model adjusted by multivariable Cox proportional hazard models. We included 6927 patients consisting of an underweight (n = 386), normal weight (n = 3785), overweight (n = 2174), and obese (n = 582) groups. The median follow-up period was 3.9 years. In the underweight group, the adjusted hazard ratios (HRs) for all-cause death and ischemic events were 1.75 (1.30-2.34) and 1.61 (1.04-2.50). The HR for all-cause death was 0.63 (0.49-0.82) in the overweight group. Restricted cubic spline regression models confirmed that lower BMI showed significantly higher risks for all-cause death and ischemic events. Conclusion Among NVAF patients taking OACs, underweight patients had higher risks of all-cause death and ischemic events than other patients. Overweight patients had lower risk of all-cause death.