Influence of obesity on outcomes in atrial fibrillation: yet another obesity paradox.

BACKGROUND: Obese patients have favorable outcomes in congestive heart failure, hypertension, peripheral vascular disease, and coronary artery disease. Obesity also has been linked with increased incidence of atrial fibrillation, but its influence on outcomes in atrial fibrillation patients has not been investigated. The objective of this research is to investigate the effect of obesity on outcomes in atrial fibrillation.

METHODS: The Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM) study was one of the largest multicenter trials of atrial fibrillation, with 4060 patients. Subjects were randomized to rate versus rhythm-control strategy. We performed a post hoc analysis of the National Heart, Lung and Blood Institute limited access dataset of atrial fibrillation patients who had body mass index (BMI) data available in the AFFIRM study. BMI data were not available on 1542 patients. Patients with BMI >or=18.5 were split into normal (18.5-25), overweight (25-30), and obese (>30) categories as per BMI (kg/m(2)). Multivariate Cox proportional hazards regression was used on the eligible 2492 patients. End points were all-cause mortality and cardiovascular mortality.

RESULTS: Over three fourths of all patients in our cohort were overweight or obese. There were 304 deaths (103 among normal weight, 108 among overweight, and 93 among obese) and 148 cardiovascular deaths (54 among normal weight, 41 among overweight, and 53 among obese) over a mean period of 3 years of patient follow-up. On multivariate analysis, overweight (hazard ratio [HR] 0.64; 95% confidence interval [CI], 0.48-0.84; P=.001) and obese (HR 0.80; 95% CI, 0.68-0.93; P=.005) categories were associated with lower all-cause mortality as compared with normal weight. Overweight (HR 0.40; 95% CI, 0.26-0.60; P <.001) and obese patients (HR 0.77; 95% CI, 0.62-0.95; P=.01) also had lower cardiovascular mortality as compared with the normal weight patients.

CONCLUSIONS: Although in prior studies, obesity has been associated with increased risk of atrial fibrillation, an obesity paradox exists for outcomes in atrial fibrillation. Obese patients with atrial fibrillation appear to have better long-term outcomes than nonobese patients.