ORIGINAL ARTICLE Ultrasound of the calcaneus and bone mineral density differs in older black and white women but is not impacted by current physical activity Ellen M. Evans Æ Kristine M. Ross Kathrine L. Heinrichs Æ Edward McAuley Karl S. Rosengren Received: 10 February 2005 / Accepted: 5 April 2005 / Published online: 15 September 2005 Ó International Osteoporosis Foundation and National Osteoporosis Foundation 2005 Abstract Black women have lower fracture rates, pri- marily due to bone-dependent factors; however, the ra- cial differences in quantitative ultrasound (QUS) for older black and white women are poorly characterized, especially in regard to the mediating effects of physical activity. The primary aim of this study was to determine if QUS measures differ in age- and body-size-matched older black and white women and to explore if the racial differences were mediated by differences in current habitual physical activity. We performed dual-energy X- ray absorptiometry (DXA) bone mineral density (BMD) measures and QUS measures [broadband ultrasound attenuation (BUA), speed of sound (SOS), quantitative ultrasound index (QUI)] of the calcaneus in 30 black and 30 white women matched in age (68.3 years) and body mass index (30.0 kg/m 2 ). Black women had greater QUS measures of SOS (1,563.6±31.7 vs 1,541.2±23.4, p=0.003) and QUI (102.6±18.5 vs 90.4±15.4, p=0.008), with a strong trend for greater BUA (79.2±15.1 vs 71.9±15.1 m/sec, p=0.066) compared with white women. As expected, black women had greater BMD measures at all sites; whole body (6.8%, p <0.010), lumbar spine (10.4%, p=0.008), proximal fe- mur (14.2%; p <0.001) and femoral neck (20.3%; p <0.001), compared with white women. Although white women reported expending 45% more energy (p=0.03) in moderate intensity physical activity than black wo- men on a weekly basis, current physical activity did not attenuate the difference in QUS measures between the races. The relations between QUS and BMD measures were similar in black compared with white women. After controlling for BMD, the racial differences in QUS measures were not apparent, precluding the conclusion that bone quality independently contributes to the reduction in fracture risk in older black women. The impact of current physical activity on QUS measures in older black and white women is negligible. Keywords Bone ultrasound Æ Ethnicity Æ Race Introduction Racial differences exist in osteoporotic fracture risk, with black women having less than half the incidence than that experienced by white women [1]. This racial disparity in osteoporotic fracture risk is due predomi- nantly to bone-dependent factors including attainment of a higher peak bone mass and potentially a slower rate of bone loss, especially cancellous bone in black women [2–4]. This larger bone mass may be related to larger skeletal muscle mass in black versus white postmeno- pausal women [4,5]. In addition to bone mass and den- sity measures, it has been suggested that older black women have a better microarchitecture or a higher bone ‘‘quality,’’ as determined by quantitative ultrasound (QUS) [6]; however, this finding is not consistent in the literature [7] and may not be independent of bone min- eral density (BMD). Habitual physical activity is a known determinant of bone health as measured by dual energy X-ray absorp- tiometry (DXA) and QUS in midlife and older women [8,9]. It is documented in the literature that blacks en- gage in less leisure-time physical activity than white women [10]. Specifically, being older, female, black, and socio-economically disadvantaged is linked to higher levels of physical inactivity [11]. Osteoporos Int (2005) 16: 1755–1760 DOI 10.1007/s00198-005-1918-0 E.M. Evans (&) Æ K.M. Ross Æ K.L. Heinrichs E. McAuley Æ K.S. Rosengren Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, 906 S. Goodwin Avenue, 215 Freer Hall, MC-052, Urbana, IL 61801, USA E-mail: elevans@uiuc.edu Tel.: +1-217-3336768 Fax: +1-217-2447322