Abstract 156: Body Mass Index and Outcomes among Patients with Atrial Fibrillation from the ATRIA2-CVRN Study

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Atrial fibrillation (AF) is a strong, independent risk factor for stroke, CVD-related mortality, and other cardiovascular complications. While studies have reported associations between higher BMI and AF incidence, few have examined the risk of thromboembolic and bleeding outcomes attributable to overweight or obesity in AF patients. We examined the longitudinal effect of BMI on all-cause mortality, as well as thromboembolic and major bleeding events, in a large cohort of incident AF patients from Kaiser Permanente Northern and Southern California. Outcomes include stroke (STR), STR and/or any other thromboembolic event (OTE), STR and/or intracranial hemorrhage (ICH), ICH and/or any other bleed (OBL). BMI (kg/m 2 ) measured nearest AF diagnosis, and demographic and clinical covariates were extracted from electronic health records and administrative databases. BMI was categorized as underweight (BMI < 18.5), normal weight (18.5 < BMI < 25), overweight (25 < BMI < 30), moderately obese (30 < BMI < 40) or extremely obese (BMI > 40). Multivariable Cox proportional hazard models were used to estimate the effect of BMI on time to event, during off-warfarin periods, adjusted for age, sex, race/ethnicity, and history of hypertension, diabetes and coronary artery disease. Among 22,487 AF patients (46% female; 6% Black, 12% Hispanic, 7% API) with off-warfarin time during follow-up, 34% were overweight, 29% obese and 6% extremely obese. Mean age ± SD was 72 ± 13 years. Median (IQR) length of off-warfarin follow-up was 1.38 (1.57) years. Crude all-cause mortality and incident thromboembolic and bleeding rates were highest among underweight or normal weight patients and gradually declined with increasing BMI (Table; all P-trend < 0.002). The unadjusted relative risks for all outcomes were substantially and significantly lower with increasing BMI (Table). However, after adjustment for demographic and clinical confounders, only risk of all-cause mortality was significantly lower for overweight and moderately obese compared to normal weight patients (Table). In conclusion, overweight and moderate obesity appear protective for all-cause mortality in at-risk AF patients during off-warfarin periods, but these effects do not appear to be mediated by reduced risk of thromboembolism or major bleeding.