Associations Between Visceral Fat, Abdominal Muscle, and Coronary Artery Calcification: A Cross-Sectional Analysis of the Multi-Ethnic Study of Atherosclerosis

BACKGROUND The associations of body composition components, including muscle and adipose tissue, and markers of subclinical coronary artery disease are unclear. We examined the relationship between abdominal CT-derived measures of the area and density of fat and muscle with coronary artery calcification (CAC), using data from the Multi-Ethnic Study of Atherosclerosis (MESA). METHODS A randomly selected total of 1,974 MESA participants free of coronary heart disease underwent abdominal CT scans at exams 2 or 3, with the resulting images interrogated for abdominal body composition. Using six cross-sectional slices spanning L2-L5, Medical Imaging Processing Analysis and Visualization (MIPAV) software was used to determine abdominal muscle and fat composition by utilizing appropriate Hounsfield units (HU) ranges. CT chest scans were used to obtain CAC scores, calculated using the Agatston method and spatially weighted calcium score (SWCS). Multivariable linear and logistic regression analysis was performed to assess the relationship between both abdominal visceral fat and muscle area and density to prevalent CAC. RESULTS A total of 1,089 participants had a CAC>0, with an average CAC score of 310. In the fully adjusted model, for every 10 cm2 increase in visceral fat area, the likelihood of having a CAC >0 increased by 0.60% (p<0.001). In the minimally adjusted model, abdominal muscle area was significantly associated with CAC>0, which became non-significant in the fully adjusted model. For density of visceral fat, every 1 HU increase (less lipid dense fat tissue), the likelihood of having a CAC score>0 decreased by 0.29% (p<0.05). No significant relationship was observed between density of abdominal muscle and CAC>0. CONCLUSION Greater area and higher lipid density of abdominal visceral fat was associated with an increased likelihood of having CAC, while there was no significant relationship between abdominal muscle area or density and CAC. Both the quantity and the quality of fat have associations with an important marker of subclinical atherosclerosis, CAC, and their significance with respect to cardiovascular outcomes requires further evaluation.