, Volume 23, Issue 4, pp 1381-1390
Date: 17 Sep 2011

Ethnic differences in composite indices of femoral neck strength

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Abstract

Summary

Bone mineral density does not explain race/ethnicity differences in hip fracture risk. In this study, we demonstrated that race/ethnicity differences in composite hip strength indices were consistent with documented race/ethnicity differences in hip fracture risk, suggesting that unlike bone density, the composite indices may represent ethnicity-independent measures of bone strength.

Introduction

African–American and Asian women have lower risks of hip fracture than Caucasian women, but such racial/ethnic variation in hip fracture risk cannot be explained by bone mineral density (BMD). The composite indices of femoral neck strength integrate femoral neck and body size with BMD and predict hip fracture risk in Caucasian women. We hypothesize that unlike race/ethnic differences in BMD, race/ethnic differences in the composite strength indices would be consistent with race/ethnic differences in hip fracture risk.

Methods

We studied a community-based sample of Caucasian (n = 968), African–American (n = 512), Chinese (n = 221), and Japanese (n = 239) women, premenopausal or in early perimenopause, from the Study of Women's Health Across the Nation.

Results

Unadjusted indices were similar in Caucasian and African–American women but higher in Asian women. After adjusting for age, body mass index, and menopause status, all three minority groups had higher composite strength indices than Caucasian women. Foreign-born Japanese women had higher unadjusted and adjusted composite strength indices than US-born Japanese women, but such differences by nativity were not observed in Chinese women.

Conclusion

We concluded that composite strength indices have the potential to explain racial/ethnic differences in hip fracture risk, suggesting that composite strength indices may represent ethnicity-independent measures of bone strength. This contention needs to be verified by further research on the fracture predictive ability of composite strength indices in multi-ethnic longitudinal cohorts.

An erratum to this article can be found at http://dx.doi.org/10.1007/s00198-011-1887-4.