Objective: Cross-sectional analyses have shown strong associations between muscle size and both bone geometry and strength. There is little data on the effect of muscle size on changes in bone structure over time. We investigated this using a well phenotyped cohort of older men and women.
Methods and Methods: We studied 194 men and 178 women from the Hertfordshire Cohort Study each of which underwent peripheral quantitative computed tomography (pQCT) of the radius (66%) and tibia (14%) in 2004-5 and then again in 2011-12. Percentage change per year was calculated for muscle cross-sectional area (CSA) and diaphyseal bone parameters (total area (Tt.Ar), cortical area (Ct.Ar), cortical density (Ct.BMD), and polar stress strain index (SSIp)).
Results: The mean(SD) age of men and women at baseline was 68.9 and 69.3 years respectively. Mean(SD) follow up time was 7.17(0.39)years. Tt.Ar increased with age and at a greater rate in men than women in the radius (median: men 1.53%/year, women 0.94%/year, p<0.001). In both the radius and tibia, Ct.Ar reduced more rapidly in women than men (radius median: men 0.17%/year, women 0.49%/year, p<0.001). Rates of muscle loss were similar in men and women (forearm: men 0.75%/year, women 0.71%/year p=0.424). In men, rate of loss of Ct.Ar was positively associated with rate of loss of muscle CSA (β(95%CI): radius 0.31(0.17,0.45) p<0.001; tibia 0.18(0.03,0.33), p<0.05). A similar trend was shown in women but did not reach significance. Baseline muscle CSA was not associated with the rate of change in Ct.Ar.
Conclusion: Changes in diaphyseal bone structure with age differ in men and women. In men, the rate of loss of Ct.Ar is associated with rate of loss of muscle CSA and not its baseline level. This suggests that interventions to maintain muscle mass may help to ameliorate the age-related deterioration in bone health.