Racial/ethnic differences in bone mineral density, muscle function and fat mass in young women

Abstract

Background: Racial/ethnic differences in bone mineral density(BMD) result in increased susceptibility of some ethnic groupsto fragility fractures in comparison to others. Conventionally,both lean mass and fat mass provide mechanical loadingto the skeleton and increase BMD, however, increase in fatmass beyond a certain level without a concurrent increasein muscle mass/strength, is detrimental to the skeleton. Theaim of this study was to determine racial/ethnic differencesin BMD, muscle function and fat mass in 18-30-year-oldwomen of Caucasian, East-Asian, South-Asian, Hispanic andAfrican-American backgrounds. Materials and methods: Forty-six women participated in the study. The visits includedsigning a written informed consent and questionnaires toassess health status, menstrual history, physical activity andcalcium intake. Body composition (fat mass, bone free leanbody mass (BFLBM), and bone mineral content (BMC)) andtotal and regional BMD were measured using Dual EnergyX-Ray Absorptiometry, while handgrip test, jump test, 1Repetition-Maximum leg press test, and bilateral isokinetic testingof knee flexors and extensors were used to quantify lower limbmuscle strength and power. Results: African-American womenhad a higher BMD at the left and right trochanter (p=0.03) andhigher BMC at several sites in comparison to South-Asians(p=0.02) and Hispanics (p=0.03). South-Asian women had ahigher fat mass (p=0.04) and percent body fat (p=0.003), andlower BFLBM (p=0.04) and strength (p=0.003) than East-Asiansand Caucasians. Conclusion: This type of research is essentialto identify at-risk minorities and fundamental for creatingawareness, developing ethnicity-specific diagnostic criteria,and preventative and therapeutic strategies.Keywords: DXA; Osteoporosis; Body composition;Premenopausal; Lean mass; Muscle strength.