Determinants of Bone Mineral Density in Postmenopausal Women: The Role of Lean and Fat Mass by Dual Energy X-Ray Absorptiometry Assessment.

BACKGROUND

Bone mineral density (BMD) is a key predictor of fracture risk in postmenopausal women. Evidence on the influence of fat and lean mass (LM) on BMD remains contradictory. This study aimed to assess the associations between BMD at different sites (whole-body, upper, and lower limbs) and anthropometric and body composition variables measured by dual energy X-ray absorptiometry (DXA) in postmenopausal women.

METHODS

A cross-sectional study was conducted on 308 healthy postmenopausal women. Anthropometric data and whole-body DXA scans were used to measure BMD, total fat mass (FM), LM, appendicular LM index (ALMI), and abdominal fat. Pearson or Spearman correlation analyses were used according to variable distribution, and a correlation matrix along with variance inflation factor analyses was used to reduce 18 variables to a final set of 5. Multiple linear regression models were built for BMD at each site.

RESULTS

Age was negatively correlated with BMD at all sites. Total LM and ALMI demonstrated positive correlations with BMD, whereas body mass index (BMI) and abdominal fat exhibited weaker positive associations. In multivariable analyses, age was negatively associated with whole-body BMD, while total LM was positively associated. For lower-limb BMD, age and total LM were significant predictors, with BMI showing a positive but weaker association. For upper-limb BMD, total LM, and ALMI were all positively associated. The models demonstrated satisfactory fit (adjusted R², 0.341-0.438; global P<0.0001).

CONCLUSIONS

Age and total LM were independently and consistently associated with BMD in postmenopausal women, whereas FM and BMI had a limited impact.