Rapid postmenopausal loss of total body and regional bone mass in normal southern Chinese females in Hong Kong.

Osteoporosis is a major health problem in Hong Kong, affecting about 200,000 patients among a population of 6 million. To evaluate the rate of bone loss and determinants of low bone mass among the Southern Chinese, we measured the total body and regional bone mass with the XR-26 dual-energy X-ray absorptiometry in 90 normal females. The results show that the total and regional bone densities were stable before menopause, with a change of around 0.5% every year. After menopause, a rapid loss is evident for total body and regional bone mass. The rate of bone loss varies from 1.2% for the pelvis to 3.1% for the Ward's triangle per year. Thus, by the age of 70, most Southern Chinese females would have lost at least 25% of their bone. Age, body weight, and skeletal area are important determinants for the total body bone mass. Bone densities in weight-bearing regions, including hip, pelvis, spine and legs correlate strongly with each other (r = 0.68, P less than 0.001). Correlation is poor among unrelated regions, such as between head and arms (r = 0.39, P greater than 0.5). To conclude, normal Chinese women in Hong Kong lose bone rapidly after menopause at a rate of about 2% per year. This may account for the major incidence of osteoporosis-related complications in Hong Kong.