Association of Body Composition and Physical Activity with Proximal Femur Geometry in Middle-Aged and Elderly Afro-Caribbean Men: |
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Authors: | LM Semanick TJ Beck JA Cauley VW Wheeler AL Patrick CH Bunker JM Zmuda |
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Institution: | (1) Department of Radiology, Johns Hopkins University, USA;(2) Department of Epidemiology, Graduate School of the Public Health, University of Pittsburgh, 130 DeSoto Street, Pittsburgh, PA 15261, USA;(3) Tobago Health Studies Office, Scarborough, Tobago |
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Abstract: | Osteoporotic fractures are less prevalent in African Americans than in caucasians, possibly because of differences in bone
structural strength. Bone structural adaptation can be attributed to changes in load, crudely measured as lean and fat mass
throughout life. The purpose of this analysis was to describe the associations of leg lean mass, total body fat mass, and
hours walked per week with femoral bone mineral density (BMD) and bone geometry in a cross-sectional sample of 1,748 men of
African descent between the ages of 40 and 79 years. BMD, section modulus (Z), cross-sectional area (CSA), and subperiosteal
width were measured from dual energy X-ray absortiometry (DXA) scans using the hip structural analysis (HSA) program. Multiple
linear regression models explained 35% to 48% of the variance in bending (Z) and axial (CSA) strength at the femoral neck
and shaft. Independent of all covariates including total body fat mass, one standard deviation increase in leg lean mass was
significantly associated with a 5% to 8% higher Z, CSA, and BMD (P < 0.010) at the neck and shaft. The number of hours walked per week was not a strong or consistent independent predictor
of bone geometry or BMD. We have shown that weight is the strongest independent predictor of femur BMD and geometric strength
although the effect appears to be mediated by lean mass since leg lean mass fraction and total body fat mass fraction had
significant and opposing effects at the narrow neck and shaft in this group of middle aged and elderly men. |
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Keywords: | African ancestry Body composition Femur geometry Men Osteoporosis |
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