Obesity is associated with increased risk of developing atrial fibrillation (AF). Different fat depots may have differential associations with cardiac pathology. We examined the longitudinal associations between pericardial, intrathoracic, and visceral fat with incident AF. We studied Framingham Heart Study Offspring and Third-Generation Cohorts who participated in the multidetector computed tomography substudy examination 1. We constructed multivariable-adjusted Cox proportional hazard models for risk of incident AF. Body mass index was included in the multivariable-adjusted model as a secondary adjustment. We included 2,135 participants (53.3% women; mean age 58.8 years). During a median follow-up of 9.7 years, we identified 162 cases of incident AF. Across the increasing tertiles of pericardial fat volume, age- and gender-adjusted incident AF rate per 1,000 person-years of follow-up were 8.4, 7.5, and 10.2. Based on an age- and gender-adjusted model, greater pericardial fat (hazard ratio [HR] 1.17, 95% confidence interval [CI] 1.03 to 1.34) and intrathoracic fat (HR 1.24, 95% CI 1.06 to 1.45) were associated with an increased risk of incident AF. The HRs (95% CI) for incident AF were 1.13 (0.99 to 1.30) for pericardial fat, 1.19 (1.01 to 1.40) for intrathoracic fat, and 1.09 (0.93 to 1.28) for abdominal visceral fat after multivariable adjustment. After additional adjustment of body mass index, none of the associations remained significant (all p >0.05). Our findings suggest that cardiac ectopic fat depots may share common risk factors with AF, which may have led to a lack of independence in the association between pericardial fat with incident AF.
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