Age-Specific Association Between Body Mass Index and the Incidence of Atrial Fibrillation in Japanese Men

Background: Obesity is reportedly associated with the incidence of atrial fibrillation (AF), but the patterns of age-specific associations between body mass index (BMI) and the risk of AF are unknown. Methods and Results: We analyzed 10,921 Japanese men without AF from a cohort of employees undergoing annual health examinations. During a follow-up period of 5.0±3.8 years, the incidence of AF was 118 (2.18/1,000 person-years). Using a multivariable Cox regression analysis, high BMI was associated with a risk of AF (hazard ratio; 1.07 by 1 unit change of BMI, 95% confidence interval [CI] 1.00–1.13, P=0.05) overall, and the effect of BMI on AF incidence changed with age (P for interaction=0.08); with subjects aged <65 years with BMI <25 as the reference, HR 0.74 (95% CI 0.47–1.17) in subjects aged <65 years with BMI ≥25, HR 2.98 (95% CI 1.36–6.54) in subjects aged ≥65 years with BMI <25, and HR 6.50 (95% CI 2.58–16.38) in subjects aged ≥65 years with BMI ≥25. The 5-year probability of AF incidence in subjects aged <65 years was 0.87% with BMI <25 and 0.64% in those with BMI ≥25, and in subjects aged ≥65 years it was 2.58% with BMI <25 and 5.53% with BMI ≥25. Conclusions: Our results indicated that the effect of BMI on AF incidence changes with age among Japanese men. Both physicians and cardiologists need to integrate advice on lifestyle measures, particularly for elderly obese men, into their daily medical routine.