The aim of this study was to investigate the association of body mass index (BMI) with mortality and cardiovascular events in Chinese patients with atrial fibrillation (AF).

This study consecutively enrolled AF patients presenting to an emergency department at 20 hospitals in China from November 2008 to October 2011. A total of 2,016 AF patients was enrolled, and patients were categorized as underweight (BMI <18.5), normal (BMI 18.5 to <24), overweight (BMI 24 to <28), and obese (BMI ≥28 all kg/m²). Multivariate Cox proportional hazards regression was used on all the patients. End points of the analyses were all-cause mortality, cardiovascular mortality, and combined end events. Among overall patients, mean BMI was 23.5 ± 3.6 kg/m²; 279 (13.8 %) patients died during 12-month follow-up, and so did 23.2 % underweight, 16.3, 9.5 and 9.2 % normal weight, overweight, and obese patients, respectively (P < 0.001). Cardiovascular mortality was 8.3% in all patients, and in underweight, normal weight, overweight and obese categories were 16.5, 9.0, 5.4 and 6.9 %, respectively (P < 0.001). On multivariate analysis, as continuous variable, BMI was not a risk factor for all-cause mortality in AF patients (hazard ratio [HR] 0.94; 95 % confidence interval [CI] 0.91–0.97; P = 0.001). As categorical variable, underweight (HR 1.57, 95 % CI 1.02–2.42, P = 0.041) and normal weight (HR 1.53, 95 % CI 1.13–2.06, P = 0.005) categories were associated with higher all-cause mortality as compared with overweight category. Underweight (HR 2.01, 95 % CI 1.76–3.43, P = 0.011) and normal weight patients (HR 1.53, 95 % CI 1.03–2.28, P = 0.037) also had higher cardiovascular mortality as compared with the overweight category.

Obesity and overweight were not risk factors for 12-month mortality in Chinese AF patients. Overweight AF patients have better survival and outcomes than normal weight (BMI 18.5–24 kg/m²) and underweight patients.