Age-related differences in total and regional bone mass: a cross-sectional study with DXA in 429 normal women.

Total body bone mineral content (TBBMC), total body bone mineral density (TBBMD) and regional bone mineral content (BMC) and density (BMD) were assessed by dual-energy X-ray absorptiometry (DXA) in 429 normal women aged 15-83 years, of whom 242 were premenopausal and 187 postmenopausal. The population was divided into 5-year age groups. In the premenopausal women no changes in TBBMC, TBBMD or regional BMC and BMD were observed with age, and TBBMC and TBBMD values correlated well with body weight (p < 0.001). Postmenopausal women showed an overall reduction in bone mass (p < 0.001), more marked at the axial level than peripherally (1.6% vs. 0.8%/year). The values of TBBMC and TBBMD correlated well with chronological age, time since the onset of menopause and body weight (p < 0.001). In these women age did not correlate with body weight, which suggests that postmenopausal bone mass loss depends more on chronological age and time since the onset of menopause than on other variables. The stability observed in bone mass values from ages 15-19 to menopause highlights the importance of stimulating the acquisition of an appropriate peak bone mass in women before adolescence begins.