Kristin L Popp1, Julie M Hughes2, Adriana Martinez-Betancourt3, Matthew Scott3, Victoria Turkington3, Signe Caksa3, Katelyn I Guerriere2, Kathryn E Ackerman4, Chun Xu5, Ginu Unnikrishnan5, Jaques Reifman5, Mary L Bouxsein6. 1. Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, THR-1051, Boston, MA 02114, USA. Electronic address: kpopp@mgh.harvard.edu. 2. Military Performance Division, United States Army Research Institute of Environmental Medicine, 10 General Greene Ave, Natick, MA 01760, USA. 3. Endocrine Unit, Massachusetts General Hospital, 50 Blossom Street, THR-1051, Boston, MA 02114, USA. 4. Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, THR-1051, Boston, MA 02114, USA; Division of Sports Medicine, Boston Children's Hospital, 319 Longwood Avenue, Boston, MA, USA 02115. 5. Department of Defense Biotechnology High Performance Computing Software Applications Institute, United States Army Medical Research and Materiel Command, 2405 Whittier Drive, Suite 200, Frederick, MD 21702, USA. 6. Endocrine Unit, Massachusetts General Hospital, Harvard Medical School, 50 Blossom Street, THR-1051, Boston, MA 02114, USA; Center for Advanced Orthopedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, One Overland Street, Boston, MA 02215, USA; Department of Orthopedic Surgery, Harvard Medical School, One Overland Street, Boston, MA, 02215, USA.
Abstract
Lower rates of fracture in both Blacks compared to Whites, and men compared to women are not completely explained by differences in bone mineral density (BMD). Prior evidence suggests that more favorable cortical bone microarchitecture may contribute to reduced fracture rates in older Black compared to White women, however it is not known whether these differences are established in young adulthood or develop during aging. Moreover, prior studies using high-resolution pQCT (HR-pQCT) have reported outcomes from a fixed-scan location, which may confound sex- and race/ethnicity-related differences in bone structure. PURPOSE: We determined differences in bone mass, microarchitecture and strength between young adult Black and White men and women. METHODS: We enrolled 185 young adult (24.2±3.4yrs) women (n=51 Black, n=50 White) and men (n=34 Black, n=50 White) in this cross-sectional study. We used dual-energy X-ray absorptiometry (DXA) to determine areal BMD (aBMD) at the femoral neck (FN), total hip (TH) and lumbar spine (LS), as well as HR-pQCT to assess bone microarchitecture and failure load by micro-finite element analysis (μFEA) at the distal tibia (4% of tibial length). We used two-way ANOVA to compare bone outcomes, adjusted for age, height, weight and physical activity. RESULTS: The effect of race/ethnicity on bone outcomes did not differ by sex, and the effect of sex on bone outcomes did not differ by race/ethnicty. After adjusting for covariates, Blacks had significantly greater FN, TH and LS aBMD compared to Whites (p<0.05 for all). Blacks also had greater cortical area, vBMD, and thickness, and lower cortical porosity, with greater trabecular thickness and total vBMD compared to Whites. μFEA-estimated FL was significantly higher among Blacks compared to Whites. Men had significantly greater total vBMD, trabecular thickness and cortical area and thickness, but greater cortical porosity than women, the net effects being a higher failure load in men than women. CONCLUSION: These findings demonstrate that more favorable bone microarchitecture in Blacks compared to Whites and in men compared to women is established by young adulthood. Advantageous bone strength among Blacks and men likely contributes to their lower risk of fractures throughout life compared to their White and women counterparts.
Lower rates of fracture in both Blacks compared to Whites, and men compared to women are not completely explained by differences in bone mineral density (BMD). Prior evidence suggests that more favorable cortical bone microarchitecture may contribute to reduced fracture rates in older Black compared to White women, however it is not known whether these differences are established in young adulthood or develop during aging. Moreover, prior studies using high-resolution pQCT (HR-pQCT) have reported outcomes from a fixed-scan location, which may confound sex- and race/ethnicity-related differences in bone structure. PURPOSE: We determined differences in bone mass, microarchitecture and strength between young adult Black and White men and women. METHODS: We enrolled 185 young adult (24.2±3.4yrs) women (n=51 Black, n=50 White) and men (n=34 Black, n=50 White) in this cross-sectional study. We used dual-energy X-ray absorptiometry (DXA) to determine areal BMD (aBMD) at the femoral neck (FN), total hip (TH) and lumbar spine (LS), as well as HR-pQCT to assess bone microarchitecture and failure load by micro-finite element analysis (μFEA) at the distal tibia (4% of tibial length). We used two-way ANOVA to compare bone outcomes, adjusted for age, height, weight and physical activity. RESULTS: The effect of race/ethnicity on bone outcomes did not differ by sex, and the effect of sex on bone outcomes did not differ by race/ethnicty. After adjusting for covariates, Blacks had significantly greater FN, TH and LS aBMD compared to Whites (p<0.05 for all). Blacks also had greater cortical area, vBMD, and thickness, and lower cortical porosity, with greater trabecular thickness and total vBMD compared to Whites. μFEA-estimated FL was significantly higher among Blacks compared to Whites. Men had significantly greater total vBMD, trabecular thickness and cortical area and thickness, but greater cortical porosity than women, the net effects being a higher failure load in men than women. CONCLUSION: These findings demonstrate that more favorable bone microarchitecture in Blacks compared to Whites and in men compared to women is established by young adulthood. Advantageous bone strength among Blacks and men likely contributes to their lower risk of fractures throughout life compared to their White and women counterparts.
Keywords:
Bone mineral density (BMD); Fracture risk; Gender; High resolution peripheral quantitative computed tomography (HR-pQCT); Sex; Stress fracture risk
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