Bone mineral density of American Indian and Alaska Native women compared with non-Hispanic white women: Results from the Women's Health Initiative Study

Objective: To compare bone mineral density (BMD) of American Indian/Alaska Native (AI/AN) women with that of non-Hispanic white women. Design: This cross-sectional study compared mean BMD between AI/AN women and a random sample of non-Hispanic white women matched on geographic region in the Women's Health Initiative Study, a prospective study of postmenopausal women. We analyzed baseline BMD measurements for the total hip, spine, and whole body from 139 AI/AN women and 1,431 non-Hispanic white women. Results: Unadjusted mean spine and whole body BMDs were not significantly different between the two races. Controlling for age, education, and hormone therapy use, adjusted mean BMD was similar by race among women who were underweight, normal, or obese. We found a significant interaction of race by body mass index on spine (P = 0.003) and whole body (P = 0.0003) BMD; thus, analyses were stratified by body mass index. Overweight AI/AN women had slightly lower adjusted mean whole body and spine BMD than overweight non-Hispanic white women (whole body: 0.97 vs 1.03 g/cm ², P = 0.02; spine: 0.96 versus 1.03 g/cm², P = 0.001). Among extremely obese (body mass index: ≥40.0 kg/m²) women, adjusted mean total hip BMD was higher in the AI/AN women (1.07 vs 0.97 g/cm², respectively, P = 0.03). Conclusions: Overall, AI/AN and non-Hispanic white women had similar BMDs. This study suggests that extremely obese AI/AN women may have higher BMD at certain skeletal sites compared with extremely obese non-Hispanic white women. However, these results need to be confirmed by additional research.