Adiposity, race and bone strength
Pollock, Norman Kenneth
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To date, studies have not investigated the relationships between adiposity, race and bone strength indices measured by three-dimensional bone imaging techniques. The purpose of this research is to determine the associations between measures of adiposity and bone strength, using pQCT, and whether these relationships vary by race. The first study (Chapter 3) addresses the relationships of percent body fat and bone strength parameters, assessed by pQCT, in predominately white late adolescent females (N=115; aged 18-19 years), taking into consideration surrogates of muscle force [i.e., MCSA and bone length]. Bone measurements in normal- and high-fat groups were also compared. Results showed that excess weight in the form of fat mass does not provide additional benefits, and may potentially be negative, for bone in late adolescent females. The second study presented in Chapter 4 was conducted in 18-19 year old white (n=25) and black (n=25) females individually matched on age, height, FFST mass, and weight to determine whether there are racial differences in bone strength parameters, assessed by pQCT. Results suggested that at the tibia, differences in bone strength are evident between black and white females; however, at the radius, these differences are less clear. In Chapter 5, relations between total fat mass and pQCT-assessed trabecular and cortical bone measurements within the tibia and radius were investigated in black females (N=48; aged 18-22 years). Since height, limb lengths and surrogates of muscle loads may confound total fat mass and bone outcome variables, these fat and bone relationships were observed independent of the following variables: height, limb lengths for each respective bone site, FFST mass, and MCSA for each respective bone site. The second objective was to compare tibial and radial bone measurements between two adiposity groups defined as having normal and high percentages of body fat, before and after controlling for differences in the same confounding variables. Consistent with the adiposity and bone strength analyses in a predominately white sample of late adolescent females, these findings in black females entering adulthood also suggest that excess adiposity levels may adversely influence the overall strength of cortical bone at appendicular skeletal sites.