Vertebral fracture prevalence in women in Hiroshima compared to caucasians or Japanese in the US

Background: Although vertebral fractures are very common among elderly Caucasian women, no studies have compared the prevalence to that among Asian populations. Any observed differences in prevalence might lead to the identification of important environmental and/or genetic factors. We therefore compared the prevalence of vertebral fractures among US Caucasians to native Japanese and Japanese immigrants in Hawaii using a standardized approach. Methods: Spinal radiographs of women aged ≥50 years were obtained from native Japanese in Hiroshima, Japanese Americans in Hawaii, and North American Caucasians in Minnesota between 1982 and 1991. Fractures were defined as vertebral heights >3 standard devlations (SD) below the vertebra-specific mean. Results: Compared to Japenese-Americans, odds ratios (OR) and 95% confidence Intervals (CI) for prevalent vertebral fractures were 1.8 (95% CI: 1.3-2.5) for native Japanese women and 1.5 (95% CI: 1.1-2.1) for Minnesota Caucasians. The OR tended to be higher when comparing the prevalence of two or more fractures per person: OR =3.2 (95% CI: 2.0-5.3) for native Japanese and OR =1.9 (95% CI: 1.2-3.2) for Minnesota Caucasians. Similar results were observed for native Japanese using a fracture definition of >4 SD below the mean, but the OR for Caucasians was reduced to 1.2 (95%CI: 0.6-2.3). Conclusion: The observation that, among these three populations, hip fracture Incidence is lowest but spine fracture prevalence is greatest among native Japanese suggests that different risk factors may be responsible.