Postmenopausal Bone Loss in American Indian Women.

Abstract

Purpose: This study aimed to investigate whether American Indian heritage influences the rate at which bone loss occurs in postmenopausal women and factors that affect this response. Methods: Secondary analyses were performed on a subpopulation of women (n = 107) from the Oklahoma American Indian Women's Osteoporosis Study cohort who completed a baseline and 1-year follow-up visit. DXA scans of lumbar spine, hip and forearm, serum biomarkers, medical history, calcium intake, and physical activity were assessed at each visit. Data were stratified by American Indian heritage or blood quantum (BQ) into <50% (BQ1) and ≥50% (BQ2), and the associations between BQ and percent change in hip, lumbar spine, and forearm bone mineral content (BMC) and density (BMD) were investigated using regression analyses with p ≤ 0.05 considered significant. Results: At baseline and at the 1-year follow-up visits, participants in BQ2 had significantly higher BMD at the hip (i.e., femur neck and intertrochanter), but not at the lumbar spine or forearm. When controlling for years post menopause and baseline bone measures, no differences in BMD change were observed between BQ groups, and only the change in BMC of the hip trochanteric region was greater in BQ2 (p < 0.05) than in BQ1. When adjustments were made for environmental factors (e.g., calcium intake, physical activity, and smoking), the percent decline in BMD at the hip (i.e., intertrochanter and total hip) was significantly greater in BQ2 compared with BQ1. Physical activity accounted for the greatest variance. Conclusions: In this cohort, postmenopausal women with American Indian heritage had a higher BMD at some regions of the hip, but they experienced bone loss at a similar rate to non-Hispanic White women. Maintenance of a physically active lifestyle was especially important in this population.