Bone mineral density in elderly Chinese: effects of age, sex, weight, height, and body mass index

To enhance our understanding of the relationship between bone mineral density (BMD) and sex, age, body mass index (BMI), weight, and height in elderly Chinese, we studied 258 males aged 50-80 years (mean +/- SD, 62.9 +/- 6.2 years) and 193 females aged 46-75 years (59.0 +/- 6.2 years). We measured BMD at the lumbar spine (L1-L4), hip (femoral neck, trochanter, and intertrochanter), and Ward's triangle. A significant difference of age-adjusted BMD among male-female groups (P < 0.0001) was observed. After adjustment for weight, the magnitude of the sex difference in BMD was reduced at all studied skeletal sites; for example, the difference declined from 18.3% to 5.5% at the spine. There were significant differences in BMD among age-stratified groups at all the sites in both sexes (P < 0.01), except for spine BMD in males (P = 0.928). Regression analysis suggested that, with aging, greater differences of BMD distribution exist in elderly females than in males. Weight accounted for the greatest proportion of age-adjusted BMD variation (e.g., at femoral neck, R-2 = 0.17 in males) among four variables: weight, height, BMI, and a principal component formed from weight and height. These results suggested that weight decreased the sex difference in BMD in elderly Chinese. Patterns of age-related BMD distribution and BMD change among different age groups differed between the sexes and between the studied sites. Weight accounted for most of the effect of two correlated variables (weight and height) on BMD in our sample.