Publications

A novel approach to ageing studies assessed the discriminatory ability of a combination of routine physical function tests and novel measures, notably muscle mechanical properties and thigh composition (ultrasound imaging) to classify healthy individuals according to age and gender. The cross-sectional study included 138 community-dwelling, self-reported healthy males and females (65 young, mean age ± SD = 25.7 ± 4.8 years; 73 older, 74.9 ± 5.9 years). Handgrip strength; quadriceps strength; respiratory peak flow; timed up and go; stair climbing time; anterior thigh tissue thickness; muscle stiffness, tone, elasticity (Myoton technology), and self-reported health related quality of life (SF36) were assessed. Stepwise feature selection using cross-validation with linear discriminant analysis was used to classify cases based on criterion variable derived from known effects of age on physical function. A model was trained and features selected using 126 cases with 0.92 accuracy (95% CI = 0.86–0.96; Kappa = 0.89). The final model included five features (peak flow, timed up and go, biceps brachii elasticity, anterior thigh muscle thickness, and percentage thigh muscle) with high sensitivity (0.82–0.96) and specificity (0.94–0.99). The most sensitive novel biomarkers require no volition, highlighting potentially useful tests for screening and monitoring effects of interventions on musculoskeletal health for vulnerable older people with pain or cognitive impairment.

Keywords: ageing; musculoskeletal health; physical function; physical frailty; screening

The classification approach demonstrated by the present study has advanced interpretation of data in rehabilitation research beyond the commonly used correlation and regression analysis techniques. The data provide evidence for future studies to assess the predictive ability of this battery of tests for physical function in a healthy cohort of older adults, preferably middle age to old age, to identify older adults at risk of frailty. These assessments could form a toolkit of standardised measurements for assessing MSK health in older adults.

The most sensitive novel biomarkers require no volition, highlighting potentially useful tests for screening and monitoring effects of physical activity interventions or treatment as MSK health improves for vulnerable older people with pain or cognitive impairment. Older misclassified cases who appear healthier than predicted support the need for studies of older people with different activity levels, to provide reference values for appropriate assessment so rehabilitation goals are relevant to the individuals’ activity levels.