Bone mineral density of the spine in normal Japanese subjects using dual-energy X-ray absorptiometry: effect of obesity and menopausal status.

Bone mineral density (BMD) of the lumbar spine was measured to determine normal Japanese values and to examine the effect of obesity and menopausal status on BMD. Normal Japanese subjects (N = 1,296, 1,048 women and 248 men) were examined using dual-energy X-ray absorptiometry. BMD for men peaked between age 20 and 29. For women, there was abrupt bone loss after age 50. Obese women within the same age bracket had a higher BMD than thin women after age 40-49. We determined that BMD began to decline during the irregular menstruation period before the onset of menopause. We conclude that there is a positive correlation between obesity and BMD, particularly in postmenopausal women. In addition, we found that bone loss related to menopause begins during the irregular menstruation period before menopause.