Ethnic origin and serum levels of 1 alpha,25-dihydroxyvitamin D-3 are independent predictors of coronary calcium mass measured by electron-beam computed tomography

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 racex1,25(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.