Background: 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).
Methods and results: 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/m(2)). 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/m(2); 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.
Conclusions: 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/m(2)) and underweight patients.