Hong Kong has the highest incidence of hip fracture in Asia, while mainland China still has very low incidence of hip fracture. However, it has been predicted there will be a major epidemic of hip fracture in China. The objective of the currect study is to compare the bone mineral density at the hip between a large population sample of Hong Kong and mainland Chinese women, so that insight can be gained into the etiology of hip fracture. This is the larger study of it's kind to date.
7130 ambulatory Hong Kong Chinese women and 7037 mainland Chinese women living in Beijing (aged 50 to 96) were recruited from the community. BMD was measured by Lunar Prodigy Advance Whole Body Bone Densitometers. Cross calibration was carried out by a phantom. The prevalence of osteoporosis was calculated according to the World Health Organization criteria. BMD at the total spine and femoral neck were adjusted for age, height and weight and compared between the 2 populations.
According to published data, the incidence rate of hip fracture was 465/100,000 in Hong Kong Chinese women and 229/100,000 in Beijing Chinese women. The prevalence of osteoporosis at the total hip in our study was 24.8% in Hong Kong Chinese women and 20% in Beijing Chinese women. After adjustment for age, height and weight, the BMD of Hong Kong Chinese women was 2.8% higher at the hip than Beijing Chinese women.
The difference in hip fracture incidence between Hong Kong Chinese and Beijing Chinese women cannot be explained by difference in BMD. Further research should focus on better measurement of bone strength in Chinese women, as well as extraskeletal factors for hip fracture, so that recommendations can be made to prevent the imminent epidemic of hip fracture in mainland China.