ETHNIC-ORIGIN AND SERUM LEVELS OF 1-ALPHA,25-DIHYDROXYVITAMIN D-3 AREINDEPENDENT PREDICTORS OF CORONARY CALCIUM MASS MEASURED BY ELECTRON-BEAM COMPUTED-TOMOGRAPHY

Background Blacks have been found to have lower amounts of coronary ca lcium as well as higher levels of the osteoregulatory steroid 1,25-dih ydroxyvitamin 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 [1 8%] black, 232 [82%] white). Black subjects had lower masses of corona ry 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). Lo g 1,25(OH)(2)D-3 levels were inversely proportional to log-transformed calcium mass (r=-.19; P=.001) in both races. Multivariate linear regr ession demonstrated that both black race (P=.02) and 1,25(OH)(2)D-3 le vels (P=.007) contributed inversely and independently to coronary calc ium mass. However, an interaction term of racex1,25(OH)(2)D-3 did not significantly contribute to coronary calcium mass, indicating that oth er undetermined factors in addition to 1,25(OH)(2)D-3 are responsible for ethnic differences in coronary calcium mass, Conclusions Both blac k race and serum levels of 1,25(OH)(2)D-3 are independent negative det erminants of coronary calcium mass. Nevertheless, diminished amounts o f coronary calcium in blacks are not accounted for by higher 1,25(OH)( 2)D-3 levels.