Bone Density and Body Composition in Japanese Women

Total body bone mineral content (BMCTB in g) and density (BMDTB in g/cm2) and body composition were measured in 1006 healthy Japanese women aged 20-79 years using dual X-ray absorptiometry. Peak BMDTB was 1.11 +/- 0.05 g/cm2 in women 20-49 years, and mean BMDTB was 1. 019 g/cm2 in the 6th decade, 0.956 g/cm2 in the 7th decade, and 0. 900 g/cm2 in the 8th decade. BMDTB declined by 0.007 g/cm2/year in women after age 50. This age-related decline in BMD showed a similar pattern to that seen for the lumbar spine and femoral neck, but the actual rate of loss was lower for BMDTB than for these other measurement sites. There was no significant difference between a eumenorrheic premenopausal group and a group with irregular menses. BMCTB and BMDTB were associated with body build, lean tissue mass, and fat mass (r = 0.29 approximately 0.65 and 0.26 approximately 0.41, respectively). Bone mass and density decreased significantly in older women of all body builds. Premenopausal Japanese women had a 5% lower BMDTB than U.S. and European whites, but the difference was several times greater in postmenopausal than in premenopausal women.