Difference in the relative contribution of lean and fat mass components to bone mineral density with generation.

Aim: To investigate whether the relative contribution of body composition (lean and fat mass component) to bone mineral density (BMD) differs depending on generation or menopause.

Methods: Subjects were 302 premenopausal women aged 30-49 years old and 197 postmenopausal women aged 50-69 years old. They were classified into four subgroups with 10-year increments. Age, height, weight and years since menopause (YSM) were recorded. Lumbar spine (L2-4), total body BMD, body fat mass, lean body mass (LBM), and the percentage of body fat (%fat) were measured using dual-energy X-ray absorptiometry. The correlation of body composition with BMD was investigated.

Results: The mean age at menopause was 50.2 +/- 4.1 years old. On Pearson's correlation test, LBM was positively correlated with BMD of the two sites in all groups. In a group aged 60-69 years, both the %fat and body fat mass were correlated with BMD. On multiple regression analysis, LBM was the principal BMD determinant in women aged less than 60 years, while body fat mass and percentage fat were the principal BMD determinants in women aged 60-69 years. Mean %fat in the group aged 60-69 years was 35.5 +/- 7.3%, which was significantly higher than that in the group aged 50-59 years (33.0 +/- 6.7%, P < 0.05).

Conclusion: Although LBM still influences BMD up to 10 years after menopause, the body fat mass initially influences BMD after 60 years of age. These difference may be attributable to certain aging-related factor(s).