Areal and volumetric bone density in Hong Kong Chinese: a comparison with Caucasians living in the United States

It is a common perception that Asians have lower bone density than Caucasians. However, such relationships could be confounded by bone size. In this study, the skeletal status of a convenience sample of 482 men and 887 women living in Hong Kong is compared with published data for Caucasians living in Rochester, Minnesota. Areal bone mineral density (BMD, g/cm²) and volumetric bone mineral apparent density (BMAD, g/cm³) were determined for the lumbar spine and proximal femur, using the Hologic QDR 2000 instrument. Cross-calibration was performed by measuring a common phantom, and the Hong Kong data were adjusted by a multiplication factor. Lumbar spine and femoral neck BMD and BMAD of Chinese men and women were all significantly lower (P<0.001 by t-test) than those of Caucasians, but the differences in BMAD were on average only about half the size of the differences in BMD. For instance, in postmenopausal Chinese women, BMD at the femoral neck and lumbar spine were 15.2% and 18.8% lower respectively, but BMAD at the femoral neck and lumbar spine were only 7.8% and 12.4% lower respectively. Similar trends were observed in men. After adjusting for age, body height and weight, the difference in BMAD between Caucasians and Chinese was further reduced and only statistically significant among postmenopausal women and among men younger than age 50 years for the lumbar spine. For instance, the adjusted BMAD in postmenopausal Chinese women at the femoral neck and lumbar spine were 3.9% (P=0.03 by ANCOVA) and 7.3% (P<0.001 by ANCOVA) lower respectively, while the adjusted BMAD at the lumbar spine for Chinese men younger than 50 years was 11.7% lower (P<0.01 by ANCOVA). Predictors of BMAD in Hong Kong Chinese women include body weight, age at menarche, cigarette smoking, and oral contraceptive use (P<0.001), while body weight was the only independent predictor of BMAD in Hong Kong Chinese men (P<0.001). We conclude that bone density is lower in Hong Kong Chinese men and women than in Caucasians, although such differences were attenuated by adjustments for bone size, body weight and height.