Prevalence, Distribution, and Risk Factor Correlates of High Pericardial and Intrathoracic Fat Depots in the Framingham Heart Study

BACKGROUND: Pericardial and intrathoracic fat depots may represent novel risk factors for obesity-related cardiovascular disease. We sought to determine the prevalence, distribution, and risk factor correlates of high pericardial and intrathoracic fat deposits. METHODS AND RESULTS: Participants from the Framingham Heart Study (n=3312; mean age, 52 years; 48% women) underwent multidetector CT imaging in 2002 to 2005; high pericardial and high intrathoracic fat were defined on the basis of the sex-specific 90th percentile for these fat depots in a healthy reference sample. For men and women, the prevalence of high pericardial fat was 29.3% and 26.3%, respectively, and high intrathoracic fat was 31.4% and 35.3%, respectively. Overall, 22.1% of the sample was discordant for pericardial and intrathoracic fat depots: 8.3% had high pericardial but normal intrathoracic fat and 13.8% had high intrathoracic but normal pericardial fat. Higher body mass index, higher waist circumference, and increased prevalence of metabolic syndrome were more prevalent in participants with high intrathoracic fat depots than with high pericardial fat (P<0.05 for all comparisons). High abdominal visceral adipose tissue was more frequent in participants with high intrathoracic adipose tissue compared with those with high pericardial fat (P<0.001). Intrathoracic fat but not waist circumference was more highly correlated with visceral adipose tissue (r=0.76 and 0.78 in men and women, respectively; P<0.0001) than with subcutaneous adipose tissue (SAT) (r=0.46 and 0.54 in men and women, respectively; P<0.0001). CONCLUSIONS: Although prevalence of pericardial fat and intrathoracic fat were comparable at 30%, intrathoracic fat correlated more closely with metabolic risk and visceral fat. Intrathoracic fat may be a potential marker of metabolic risk and visceral fat on thoracic imaging.