The end result of a low BMD is an osteoporotic fracture. Initial estimates of osteoporosis prevalence counted hip fractures as a marker, as subjects with these fractures inevitably present to the hospitals, making ascertainment of cases more straightforward. One of the earliest studies on hip fracture in Asia came from Singapore, showing an age-adjusted rate of hip fracture of 75/100,000 in women who were 60 years of age and older.9 In Hong Kong, between 1965–1967, the rate of hip fractures was 153/100,000 in women and 96/100,000 in men.10 Between 1988–1992, the hip fracture rate in Chinese in Beijing was 87/100,000 in women and 97/100,000 in men.11 In a 1987 Japanese study, the hip fracture rate was 220–260/100,000 in 70–74-year-old-women, rising to 1180–1390/100,000 in 85–59 years olds.12 Thus, hip fractures were less common in Asians compared to Caucasians; for example, in the Rochester (American) White population, the hip fracture rate was 510/100,000 in women and 174/100,000 in men between 1965–1974.13 Interestingly, even within the same country, the different races can have different rates of hip fracture. In Singapore, hip fracture rates were higher in the Chinese and Malay, compared to the Indian population.14
These differences were maintained in subsequent later studies done in the 1990s. A study comparing five different countries including Hong Kong and Beijing done in 1990–1992 showed the age-adjusted hip fracture rate in women and men over the age of 50 were highest in Reykjavik, Iceland, followed by Hong Kong, and then Beijing, China. The rates in the three countries were 697, 428 and 96 per 100,000 women, and 349, 270, 107 per 100,000 in men, respectively.15 The 1997 figures for hip fracture in three Asean countries confirmed the trend of lower hip fracture rates in Asia. In the age-adjusted hip fracture rates per 100,000 for women, there were 442 fractures in Singapore, 269 in Thailand and 218 in Malaysia. For men, the numbers were 164 in Singapore, 114 in Thailand and 88 in Malaysia.16 Again, these figures were much lower than the US White data from 1989 presented in that paper which showed a hip fracture rate of 535/100,000 for women and 187/100,000 for men.
What these later studies also showed was that the hip fracture incidence seemed to be rising and the suggestion was that hip fracture rates increased with increasing urbanization, but exactly why it should be so has not been easy to elucidate. Certainly in Hong Kong, where there was rapid urbanization, the incidence of hip fracture was doubled between 1966 and 1985.17 Similarly, in Singapore, the hip fracture rate in women increased 5-fold from the 1960s to 1990s.14
Vertebral fractures have not been so well studied in Asia, but the story is similar, albeit the differences are not so marked. Melton found that the prevalence of vertebral fractures in a population-based sample in Minnesota, USA was 11.7% in 60–64 years olds and 16.2% in 65–69 years olds.18 In Japan, the prevalence of vertebral fracture in a population-based sample was 5.7% in 60–64 years olds and 13.0% on 65–69 years olds.19 Another study found an increased odds ratio for prevalent vertebral fractures of 1.8 (95% CI 1.3–2.5) in native Japanese women compared to Japanese-American women.20 In the Chinese in Beijing, the age-standardized prevalence of vertebral fractures was 5.5% lower compared to women in Minnesota, USA.21