Aims: Obesity has been shown to be a risk factor for first atrial fibrillation (AF), but whether it is associated with progression from paroxysmal to permanent AF is unknown.
Methods and results: In this longitudinal cohort study, Olmsted County, MN residents confirmed to have developed paroxysmal AF during 1980-2000 were identified and followed passively to 2006. The interrelationships of body mass index (BMI), left atrial (LA) size, and progression to permanent AF were analysed. Of a total of 3248 patients (mean age 71 +/- 15 years; 54% men) diagnosed with paroxysmal AF, 557 (17%) progressed to permanent AF (unadjusted incidence, 36/1000 person-years) over a median follow-up period of 5.1 years (interquartile range 1.2-9.4). Adjusting for age and sex, BMI independently predicted the progression to permanent AF (hazard ratio, HR 1.04, CI 1.03-1.06; P < 0.0001). Compared with normal BMI (18.5-24.9 kg/m(2)), obesity (30-34.9 kg/m(2)) and severe obesity (>or=35 kg/m(2)) were associated with increased risk for progression [HR 1.54 (CI 1.2-2.0; P = 0.0004) and 1.87 (CI 1.4-2.5; P < 0.0001, respectively)]. BMI remained highly significant even after multiple adjustments. In the subgroup with echocardiographic assessment (n = 744), LA volume was incremental to BMI for independent prediction of progression after multiple adjustments, and did not weaken the association between BMI and progression to permanent AF (HR 1.04; CI 1.02-1.05; P < 0.0001).
Conclusion: There was a graded risk relationship between BMI and progression from paroxysmal to permanent AF. This relationship was not weakened by LA volume, which was independent of and incremental to BMI for the prediction of progression to permanent AF.