Ethnic Origin and Serum Levels of 1α,25-Dihydroxyvitamin D 3 Are Independent Predictors of Coronary Calcium Mass Measured by Electron-Beam Computed Tomography

Abstract

Background Blacks have been found to have lower amounts of coronary calcium as well as higher levels of the osteoregulatory steroid 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] than whites. We sought to determine if racial differences in coronary calcium mass could be explained by differences in serum levels of 1,25(OH) 2 D 3 . Methods and Results We evaluated standard coronary risk factors, quantified coronary calcium mass with electron-beam computed tomography (EBCT), and measured serum 1,25(OH) 2 D 3 with radioimmunoassay in 283 high-risk subjects (51 [18%] black, 232 [82%] white). Black subjects had lower masses of coronary calcium than whites (14 versus 47 mg; P =.003). Serum 1,25(OH) 2 D 3 levels were slightly higher in blacks (41 versus 38 pg/mL; P =.05). Log 1,25(OH) 2 D 3 levels were inversely proportional to log-transformed calcium mass ( r =−.19; P =.001) in both races. Multivariate linear regression demonstrated that both black race ( P =.02) and 1,25(OH) 2 D 3 levels ( P =.007) contributed inversely and independently to coronary calcium mass. However, an interaction term of race×1,25(OH) 2 D 3 did not significantly contribute to coronary calcium mass, indicating that other undetermined factors in addition to 1,25(OH) 2 D 3 are responsible for ethnic differences in coronary calcium mass. Conclusions Both black race and serum levels of 1,25(OH) 2 D 3 are independent negative determinants of coronary calcium mass. Nevertheless, diminished amounts of coronary calcium in blacks are not accounted for by higher 1,25(OH) 2 D 3 levels.