Endocrine Abstracts

Ageing is associated with sarcopenia, osteoporosis and an increased risk of falling, which together contribute to increased fracture risk. There are few data describing the associations between functional measures of muscle and bone during ageing. Therefore, the aim of this study was to examine in ageing men associations between measures of lower-limb muscle strength and age and then to investigate the relationships with tibial bone outcomes.

Men (n=301) aged 40–85 years were recruited in the UK (201-White, 43-Black, 57-South-Asian). pQCT outcomes from the 38% tibia were: cortical bone mineral content (Ct.BMC), cross-sectional area (CSA), and cross-sectional moment of inertia (CSMI). Jumping mechanography assessed muscle force (kN) and power (kW) from a single 2-leg counter-jump. Linear regression was used to describe the relationships between: power/force and age with an ethnicity*age interaction; and force and bone outcomes; all were adjusted for weight and height. Results are expressed as β-coefficients (95%CI) of percentage unit change in age/force.

There were significant negative relationships between muscle power and age in all groups (P<0.001): White (−1.9% (−2.1, −1.7)), Black (−1.3% (−1.8, −0.8)) and South-Asian (−1.8% (−2.3, −1.3)), with a significant difference between the slopes of White and Black men (P=0.03). There was a significant negative relationship between force and age in White (−3.9% (−0.6, −0.20); P<0.0001) and South-Asian (−4.2% (−0.8, −0.08); P=0.017) but not Black men (−3.0% (−0.7, 0.8); P=0.121). Muscle force and bone outcomes were positively associated: Ct.BMC 8.5% (3.6, 13.4); CSA 9.3% (5.4, 13.2) and CSMI 18.6% (11.1, 26.2), all P<0.001; there were no ethnic differences in these relationships (with an additional age-adjustment).

The relationship between power and age was different between ethnicities which may lead to differences in fall risk. Muscle force positively predicted bone outcomes in ageing men. Together, these findings may contribute to the understanding of fracture incidence in different ethnic groups.