Difference in Muscle Quality over the Adult Life Span and Biological Correlates in the Baltimore Longitudinal Study of Aging

Abstract

Background/Objectives Previous studies demonstrated that in older persons decline in muscle strength occurs with aging more rapidly than loss of muscle mass, highlighting the importance of muscle quality for functional outcomes in later life. We examine differences in a proxy measure of muscle quality across the adult life-span and explore potential mechanisms of muscle quality change through identification of cross-sectional correlates of muscle quality. Design Cross-sectional study. Setting/Participants 786 participants from the Baltimore Longitudinal Study of Aging (mean age 66.3 years, range: 26 – 96 years). A sensitivity analysis was conducted in a subset of participants matched by sex, muscle mass and body size. Measurements Muscle quality, was operationalized as the ratio of knee-extension strength (isokinetic dynamometry) to thigh muscle cross-sectional area (computed tomography). Trends of muscle strength, area and muscle quality ratio across age were evaluated and the association of the muscle quality ratio with measures reflecting domains of cognitive function, motor control, peripheral nerve function, adiposity, glucose homeostasis, and inflammation were assessed through multivariate regression analyses. Results A linear relationship between age and muscle quality ratio was observed suggesting gradual decline in muscle quality across the adult life course. Associations were observed between muscle quality ratio and measures of adiposity as well as peroneal nerve motor conduction velocity, finger tapping speed, memory performance (p<.01). The association of muscle quality ratio with nerve conduction velocity was maintained after adjustment for anthropometrics (p<.05). Conclusion These observations suggest that muscle quality declines progressively with aging across the adult life span and is affected by both obesity and neurological factors. Studies are needed to clarify the mechanisms of these associations and their implications for functional outcomes.

Muscle strength mediates the relationship between mitochondrial energetics and walking performance

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Influence of ageing and essential amino acids on quantitative patterns of troponin T alternative splicing in human skeletal muscle

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