Ethnic, anthropometric, and lifestyle associations with regional variations in peak bone mass

The study investigated the ability of ethnicity and anthropometric and lifestyle factors to account for differences within subjects in bone mass at different skeletal sites. The subjects were young, adult, Japanese, Filipino, Hawaiian, and white women ages 25-34. In the preliminary analyses, they were divided into thirds based on their BMD z-scores. Thirty-five percent exhibited high variability in bone mass: they were in the upper third at one or more bone sites and in the lower third at one or more sites. Other women had more generalized low bone mass: 25% were in the lowest third for two or more sites, and there were no sites with low bone mass in the upper third. In subsequent analyses, ethnicity, anthropometry, and lifestyle influences were examined as possible predictors of differences in bone mineral content (BMC) between bone sites in bone-size adjusted models. White women had greater BMC at the proximal radius and calcaneus than at the distal radius compared with other ethnic groups. This may be explained by the fact that they had exceptionally wide bone widths at the distal radius. Of the anthropometric variables, fat mass was associated with higher bone mass at sites with higher proportions of cancellous tissue (calcaneus > spine > radius sites). Muscle mass was associated with greater bone mass at the calcaneus and proximal radius than at the spine. For the lifestyle variables, women with greater milk consumption between the ages of 10-24 years had higher spine bone mass than expected from their measurements at the proximal radius. Women 12-17 years of age who had been more active in sports had higher calcaneous bone mass than expected from their spine measurements. As the study participants were still young women, the results suggest that regional differences in bone mass may partly derive from anthropometric and lifestyle influences during skeletal maturation.