Body mass index and all-cause mortality in patients with atrial fibrillation: insights from the China atrial fibrillation registry study.

Background: Impact of body mass index (BMI) on all-cause mortality in atrial fibrillation (AF) patients remains controversial.
Methods: A total of 10,942 AF patients were prospectively enrolled and categorized into four BMI groups: underweight (BMI < 18.5 kg/m ² ), normal weight (BMI 18.5-24 kg/m ² ), overweight (BMI 24-28 kg/m ² ) and obesity (BMI ≥ 28 kg/m ² ). The primary outcome was all-cause mortality. Different Cox proportional hazards models were performed to evaluate the association between BMI and all-cause mortality.
Results: During a median follow-up of 30 months (IQR 18-48 months), 862 deaths events occurred. Compared to normal BMI, higher BMI was associated with a lower mortality risk (overweight: HR 0.70; 95% CI 0.61-0.81, P < 0.0001 and obesity: HR 0.54; 95% CI 0.44-0.67, P < 0.0001) and lower BMI was associated with a higher mortality risk (HR 2.23, 95% CI 1.67-2.97, P < 0.0001).
Conclusion: A reversed relationship between BMI and all-cause mortality in AF patients was found. Higher risk of mortality was observed in underweight patients compared to patients with a normal BMI, while overweight and obese patients had a lower risk of all-cause mortality.
Clinical Trial Registration: URL: http://www.chictr.org.cn/showproj.aspx?proj=5831. Unique identifier: ChiCTR-OCH-13003729.