RESUMEN
UNLABELLED: We examined the association of serum 25-hydroxyvitamin D [25(OH)D] with indices of bone quality in older men. Positive associations for 25(OH)D and bone mineral density, content, cortical thickness, and axial and polar strength strain indices were observed among Caucasians; however, among men of African descent findings were either null or negative. INTRODUCTION: There are limited data on serum 25(OH)D and bone measures in men of African ancestry. To better understand racial differences in vitamin D status and bone health, a cross-sectional study among 446 Caucasian men in the US and 496 men of African ancestry in Tobago (age ≥ 65 years) was conducted. METHODS: Serum 25(OH)D (liquid chromatography and tandem mass spectrometry) was measured, and peripheral quantitative computed tomography scans were administered. Bone measures estimated included trabecular and cortical volumetric bone mineral density (vBMD), bone mineral content (BMC), bone geometry (cross-sectional area and cortical thickness), and polar and axial strength strain indices (SSIp and SSIx). RESULTS: Men of African ancestry had higher 25(OH)D than Caucasians (34.7 vs. 27.6 ng/ml, p < 0.01). Among Caucasians, 25(OH)D was positively (p trend < 0.05) associated with cortical vBMD, total BMC, cortical thickness, SSIp, and SSIx at the distal radius after adjustment for potential confounders. Similar patterns were observed at the distal tibia. In contrast, in men of African ancestry, there was an inverse association (p trend < 0.05) between 25(OH)D and the cross-sectional area, and SSIx. Race modified (p for interaction < 0.05) the association between 25(OH)D and total BMC, cross-sectional area, SSIp, SSIx, and trabecular vBMD of the radius. In men of African ancestry, there was evidence of a threshold effect (at approximately 18 ng/ml) for 25(OH)D on tibial total BMC and cortical thickness. CONCLUSIONS: More studies are needed to better comprehend these race differences for 25(OH)D and bone density, geometry, and indices of bone strength.
Asunto(s)
Densidad Ósea/fisiología , Radio (Anatomía) , Tibia , Vitamina D/análogos & derivados , Anciano , Población Negra , Estudios Transversales , Humanos , Masculino , Pennsylvania , Radio (Anatomía)/anatomía & histología , Radio (Anatomía)/fisiología , Tibia/anatomía & histología , Tibia/fisiología , Trinidad y Tobago/etnología , Vitamina D/sangre , Población BlancaRESUMEN
BACKGROUND: Of the few exercise intervention studies focusing on pediatric populations, none have confined the intervention to the scheduled physical education curriculum. OBJECTIVE: To examine the effect of an 8-month school-based jumping program on the change in areal bone mineral density (aBMD), in grams per square centimeter, of healthy third- and fourth-grade children. STUDY DESIGN: Ten elementary schools were randomized to exercise (n = 63) and control groups (n = 81). Exercise groups did 10 tuck jumps 3 times weekly and incorporated jumping, hopping, and skipping into twice weekly physical education classes. Control groups did regular physical education classes. At baseline and after 8 months of intervention, we measured aBMD and lean and fat mass by dual-energy x-ray absorptiometry (Hologic QDR-4500). Calcium intake, physical activity, and maturity were estimated by questionnaire. RESULTS: The exercise group showed significantly greater change in femoral trochanteric aBMD (4.4% vs 3.2%; P <.05). There were no group differences at other sites. Results were similar after controlling for covariates (baseline aBMD change in height, change in lean, calcium, physical activity, sex, and ethnicity) in hierarchical regression. CONCLUSIONS: An easily implemented school-based jumping intervention augments aBMD at the trochanteric region in the prepubertal and early pubertal skeleton.