Relation of Body Mass Index and Gender to Left Atrial Size and Atrial Fibrillation.

Increased body mass index (BMI) and obesity are associated with greater risk of atrial fibrillation (AF). However, whether this correlation is independent and gender specific remains unclear. The objective of this study was to characterize the relation between BMI, left atrial (LA) size, and presence of AF and determine whether this association is gender specific. We prospectively studied 499 patients who underwent a transthoracic echocardiogram at an academic tertiary care medical center. Clinical and echocardiographic data were obtained. The primary outcome of interest was the presence of AF. Of 499 patients studied, 240 (48.1%) were men and 259 (51.9%) were women. Of these, 151 (30.1%) had normal BMI, 181 (36.3%) were overweight, and 167 (33.5%) were obese. Obese patients were younger and had larger LA diameters, LA areas (LAAs), and LA volumes (LAVs). Rates of AF were similar among the BMI classes in the overall population and in men and women separately. In multivariate analysis, BMI and gender were both independently associated with LA diameter, LAA, and LAV. Age (odds ratio 1.02, 95% CI 1.00 to 1.04, p = 0.023) and LA diameter (odds ratio 2.52, 95% CI 1.61 to 3.97, p <0.001) were the only determinants of the presence of AF in the overall population. BMI and gender were not independently associated with AF. In this observational study, our findings demonstrate that higher BMI and male gender were independently associated with greater LA diameter, LAA, and LAV. Older age and greater LA diameter were independently associated with higher rates of AF, whereas BMI and gender were not.