Gender-specific associations between physical functioning, bone quality, and fracture risk in older people.

The aim of this study was to investigate which parameters of physical functioning are associated with bone quality and fracture risk and whether gender-specific differences exist within these associations. We studied 1,486 participants of the Longitudinal Aging Study Amsterdam. As measures of physical functioning, handgrip strength, physical performance, and level of physical activity were assessed. To assess bone quality, broadband ultrasound attenuation (BUA) and speed of sound (SOS) were measured at baseline using quantitative ultrasound and bone mineral density (BMD) at baseline and after 3 years by dual-energy X-ray absorptiometry. In addition, fracture incidence over 6 years was assessed. After adjustment for confounders (age, serum 25[OH]D, smoking, and body weight), in men, physical performance was positively related to BUA, SOS, and BMD cross-sectionally and to BMD longitudinally. Using Cox proportional hazards model, in men higher handgrip strength and physical performance were associated with reduced fracture risk after adjustment for confounders (hazard ratio [HR] 0.96, 95 % confidence interval [CI] 0.92-0.99, and HR 0.89, 95 % CI 0.80-0.98, respectively). In women, a moderate level of physical activity was related to reduced fracture risk (HR 0.57, 95 % CI 0.33-0.99). In conclusion, in men, higher handgrip strength and physical performance are related to higher bone quality and reduced fracture risk, whereas in women, a moderate to high level of physical activity is associated with reduced fracture risk. These measurements may contribute to the identification of individuals at high fracture risk. Both the causality of and explanations for gender-specific differences in these relationships remain subject to further studies.