Differences in bone microarchitecture between postmenopausal Chinese‐American and white women

Chinese‐American women have lower rates of hip and forearm fracture than white women despite lower areal bone density (aBMD) by dual X‐ray absorptiometry (DXA). We recently reported higher trabecular (D_trab) and cortical (D_comp) bone density as well as greater trabecular (Tb.Th) and cortical thickness (C.Th) but smaller bone area (CSA), as measured by high‐resolution peripheral quantitative computed tomography (HR‐pQCT), in premenopausal Chinese‐American compared with white women. These findings may help to account for the lower fracture rate among Chinese‐American women but were limited to measurements in premenopausal women. This study was designed to extend these investigations to postmenopausal Chinese‐American (n = 29) and white (n = 68) women. Radius CSA was 10% smaller in the Chinese‐American versus the white group (p = .008), whereas their C.Th and D_comp values were 18% and 6% greater (p < .001 for both). Tibial HR‐pQCT results for cortical bone were similar to the radius, but Tb.Th was 11% greater in Chinese‐American versus white women (p = .007). Tibial trabecular number and spacing were 17% lower and 20% greater, respectively, in Chinese‐American women (p < .0001 for both). There were no differences in trabecular or whole‐bone stiffness estimated by microstructural finite‐element analysis, but Chinese‐American women had a greater percentage of load carried by the cortical bone compartment at the distal radius and tibia. There was no difference in load distribution at the proximal radius or tibia. Whole‐bone finite‐element analysis may indicate that the thicker, more dense cortical bone and thicker trabeculae in postmenopausal Chinese‐American women compensate for fewer trabeculae and smaller bone size. © 2011 American Society for Bone and Mineral Research.