Purpose: We investigated ethnic differences in areal bone mineral density (aBMD; g x cm(-2)) and its determinants at two levels of maturity in Asian- and Caucasian-Canadian girls.
Methods: Participants were 131 Asian (26 Tanner breast stage I (aTI) and 30 Tanner II (aTII)), and Caucasian (30 Tanner I (cTI) and 45 Tanner II (cTII)) girls. We measured calcium intake by a food frequency questionnaire, general physical activity, and extracurricular sports with a modified Physical Activity Questionnaire for Children and loaded physical activity by 7-d recall. Fat mass, lean mass, and aBMD for the total body (TB), and aBMD at the lumbar spine (LS), proximal femur (PF), femoral neck (FN), and trochanter (TR) were measured by DXA (Hologic QDR 4500). We used ANCOVA (controlling for size and lean and fat mass) to compare bone mineral content (BMC) and aBMD between ethnicities within Tanner stages.
Results: Calcium intake was significantly lower for Asian girls in both TI and TII (P < 0.001) as compared with Caucasians. For physical activity measures, only the general score was greater in cTI than aTI (P < 0.05). Participation in loaded physical activities and extracurricular sports was significantly less for aTII than cTII (both, P < 0.01), whereas general physical activity did not differ. aBMD measures were similar between aTI and cTI. However, TB, PF, FN, and aBMD were significantly lower (approximately 9-14%) in aTII as compared with cTII.
Conclusion: Thus, there was greater ethnic disparity in lifestyle factors related to bone health and absolute measures of bone mineral with advanced maturity.