Are there skeletal differences between races?
Answers
Differences in fracture risk between different racial and ethnic groups have been noted and investigated for many years. Despite this, our understanding of the basis for these differences is still incomplete. A full explanation will undoubtedly provide important insights about the etiology of osteoporosis, so additional research is clearly relevant.
In this issue of JCEM, two interesting papers from the Study of Women’s Health Across the Nation (SWAN) add to our knowledge base on these topics. Finkelstein et al. (1, 2) examined bone mineral density (BMD) and bone turnover markers in a racially and ethnically mixed sample of more than 2000 pre- and perimenopausal women. Data are provided separately for Chinese and Japanese women living in the United States in addition to African American and Caucasian women, which allow a direct comparison between these four groups. More notably, these studies avoid problems associated with treating Asians as a single group rather than distinct groups with different cultural backgrounds, lifestyles, and fracture rates (3, 4). Various interesting findings regarding the rank order of the different race/ethnic groups and the effect (or lack thereof) of the different explanatory factors emerged. Among the most striking findings was that ethnicity per se was not associated with differences in lumbar spine BMD in the three nonwhite groups examined. Furthermore, all three nonwhite groups had higher lumbar spine BMD than Caucasians of comparable body weight, which is noted as being consistent with observed racial and ethnic differences in vertebral fracture rates. Interestingly, even after accounting for size differences, the patterns of femur neck BMD did not mirror fracture patterns at this skeletal site quite as well, although the discrepancy was smaller than when unadjusted BMD values were compared between groups. In addition, ethnic patterns of bone marker levels did not parallel ethnic patterns of BMD, leading the authors to conclude that other factors are likely responsible for much of the ethnic variation in adult BMD.