Ethnic Variations in Serum 25(OH)D Levels and Bone Ultrasound Attenuation Measurements in Blacks and Whites.

Vitamin D deficiency is more common in Blacks, yet Blacks have lower prevalence of bone fragility fractures or osteoporosis than Whites. Broadband ultrasound attenuation (BUA) has been used to explore the association between serum 25(OH)D levels and bone quality in White and non-white populations. We investigated serum 25(OH)D status with corresponding BUA measurements assessed cross sectionally in a cohort of 232 Blacks and 260 Whites, aged 30-95 years who were part of the calibration study of the large Adventist Health Study-2 (AHS-2). At the calibration clinics, calcaneal BUA was measured and blood drawn for serum 25(OH)D assessment. In multivariable analyses, BUA was negatively associated with age (β-coefficient = -0.38; p < 0.0001) and positively associated with body mass index (BMI) (p (trend) < 0.0001) and positively, but non-significantly, associated with serum 25(OH)D levels. Also, as expected, females had lower BUA (β-coefficient = -5.19; p < 0.05) and Blacks had higher BUA (β-coefficient = 4.26; p < 0.05). Gender and race modified the relationship of serum 25(OH)D on BUA with a positive association in males (p (trend) ≤ 0.05), but no significant association in females after also controlling for menopausal status and hormone therapy. After also controlling for serum 25(OH)D levels, Black males had higher BUA than White men, but such differences were not found among the females. When stratifying on race, a positive association between serum 25(OH)D levels and BUA (p (trend) ≤ 0.05) was found in Blacks, but not among Whites. Further studies are needed to understand how racial/ethnic differences in serum 25(OH)D levels influence bone health.