The obesity paradox for outcomes in atrial fibrillation: Evidence from an exposure‐effect analysis of prospective studies

The impact of obesity on the prognosis of atrial fibrillation (AF) remains controversial. We conducted an exposure-effect meta-analysis of prospective studies to clarify the relationship between body mass index (BMI) and outcomes in patients with AF. The Cochrane Library, PubMed, and Embase databases were searched through May 1, 2019. Summary relative risks (RRs) were calculated using random-effects models. Nonlinear associations were explored using restricted cubic spline models. Twenty publications involving 161,922 individuals were included. Categorical variable analysis showed that underweight was associated with an increased risk of all-cause mortality (RR: 2.6), cardiovascular death (RR: 2.91), major bleeding (RR: 1.57), stroke or systemic embolism (RR: 1.62), and a composite endpoint (RR: 2.23). In exposure-effect analysis, the risk per 5 BMI increase was reduced for adverse outcomes (RR=0.86, 95% CI: 0.80-0.92 for all-cause death; RR=0.82, 95% CI: 0.71-0.95 for cardiovascular death; RR=0.89, 95% CI: 0.84-0.95 for stroke or systemic embolism; and RR=0.78, 95% CI: 0.67-0.92 for a composite endpoint). There was a significant "U"-shaped exposure-effect relationship with all-cause death, and the nadir of the curve was observed at a BMI of approximately 28. Our results showed that underweight is associated with a worse prognosis, but that overweight and obesity are associated with improved adverse outcomes in patients with AF.