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 Dcomp 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. (C) 2011 American Society for Bone and Mineral Research.