The Profile of Bone Mineral Density in Chinese Women: Its Changes and Significance in a Longitudinal Study

Bone mineral density (BMD) has been shown to be different in different ethnic groups. When lifestyle and diet evolve, there is a possibility of a change in the normal reference BMD values within an ethnic group over a period of time. As the osteoporotic risk uses the T-score as the bench mark, it is pertinent to evaluate whether such changes do occur. Two measurements, 5 years apart, of the BMD of the spine and the hip were made in a cohort of Chinese women in Hong Kong. A kernel function smoothing method, a nonparametric statistical method, was employed to present the BMD data. The greatest rate of bone loss was found to occur between 50 and 59 years of age, but this rate of loss was reduced from age 60 onwards. The BMD values obtained in these two measurements were different from the previous studies in the same population and were found to be higher at the lumbar spine and neck of femur in women over 65 years of age. Even within the cohort, there seemed to be a reduction in the BMD values of the hip in a span of 5 years, although the differences were statistically insignificant. These studies suggest that BMD values could change in a population for a variety of possible reasons. Hence, the reference BMD values might need to be evaluated at regular intervals for the T-score to be meaningful.