Body Mass Index and Outcomes in Atrial Fibrillation

Study Questions:

What is the effect of body mass index (BMI) on outcomes in patients with atrial fibrillation (AF)?


The data in this study were obtained from ORBIT-AF (Outcomes Registry for Better Informed Treatment of Atrial Fibrillation), a national registry of outpatients with AF. The analysis included 9,606 patients who were followed for a mean of 26.8 months. One percent of patients were underweight (BMI <18.5 kg/m2), 22% had a normal weight (BMI 18.5-<25 kg/m2), 33% were overweight (BMI 25-<30 kg/m2), 23% had class I obesity (BMI 30-<35 kg/m2), 12% had class II obesity (BMI 35-<40 kg/m2), and 10% had class III obesity (BMI ≥40 kg/m2). The primary outcome was all-cause mortality.


A rhythm-control strategy and anticoagulation were more common in the higher weight categories. The use of warfarin ranged from 69% in normal-weight patients up to 75% in patients with class III obesity. There was an inverse relationship between mortality and weight category, with a mortality rate of 8.28/100 patient-years in normal-weight patients and 3.81/100 patient-years in patients with class III obesity. After adjustment for confounding variables, the mortality risk was 7% lower for every 5 kg/m2 increase in BMI. BMI was not an independent predictor of thromboembolic events or AF progression.


The mortality risk over 2 years of follow-up in patients with AF is inversely related to body weight.


The study confirms the presence of an “obesity paradox” previously reported in patients with AF and other types of heart disease, and that remains unexplained. Nevertheless, obesity is associated with many negative outcomes, and it remains appropriate to promote weight loss in obese patients with AF.

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