Abstract P300: Cross-ethnic Differences in Ectopic Fat Depots Variably Predict Coronary Artery Calcium

Abstract

Background: Established risk factors do not fully explain racial/ethnic variations in coronary artery calcium (CAC), a measure of atherosclerotic burden that is independently associated with incident cardiovascular events. Obesity is a known CAC risk factor but common measurements like body mass index (BMI) incompletely capture known racial/ethnic differences in body composition or the complexity of ectopic fat depots. Hypothesis: We assessed whether differences in ectopic fat could further explain cross-ethnic variations in CAC after adjustment for BMI and other known risk factors. Methods: We examined the associations of four ectopic fat depots measured with computed tomography - visceral abdominal, intermuscular abdominal, intrahepatic, and pericardial - with CAC among participants ages 44-84 years without known cardiovascular disease at baseline and among five race/ethnicities: 803 South Asians, 2622 Whites, 1893 African Americans, 1496 Latinos, and 803 Chinese Americans. We harmonized data from the Multi-Ethnic Study of Atherosclerosis (MESA) with the Mediators of Atherosclerosis in South Asians Living in America (MASALA) Study, which was modeled on MESA to allow for cross-ethnic comparisons. Pooled and race/ethnicity-specific multivariable models for log-transformed CAC [ln(CAC+1)] were adjusted for age, sex, BMI, family history of heart disease, exercise, alcohol use, smoking, hypertension, cholesterol medication use, low-density lipoprotein, and diabetes. Results: After BMI-adjustment, South Asians had the highest intrahepatic fat of any race/ethnic group, while both African Americans and South Asians had the least pericardial fat. Greater amounts of ectopic fat were associated with higher CAC in each race/ethnicity for pericardial fat volume (p-for-trends in all groups<0.001), visceral abdominal (p-for-trends<0.05), and intermuscular abdominal (p-for-trends<0.05). However, only pericardial fat volume remained independently correlated (p<0.001) with CAC after multivariable adjustment. In race/ethnicity-specific models, pericardial fat significantly predicted CAC in Whites (β 0.21; p<0.001), South Asians (β 0.26; p<0.01), and African Americans (β 0.15; p<0.05), but not in Chinese Americans or Latinos. In the pooled multivariable model (N=7363), geometric CAC means were: 30 (men) and 7 (women) in Whites, 20 and 5 in South Asians, 14 and 4 in Latinos, 11 and 5 in Chinese Americans, and 10 and 4 in African Americans. Adding pericardial fat to this multivariable model minimally changed mean CAC scores. Conclusions: We found significant racial/ethnic variation in ectopic adiposity, particularly for pericardial fat, independent of BMI. However, this variation did not measurably explain cross-ethnic differences in CAC scores. A further assessment of how ectopic fat depots may variably promote cardiovascular disease is needed.