September 5, 2019, by bmillar
Muscle mass, metabolic quality and physical function in frail older people with non-weight bearing fractures.
“No decline with age is as dramatic or potentially more significant than the decline in lean body mass” (1).
In 1989 Rosenberg published this observation and coined the term sarcopenia, a description that has subsequently been extended to incorporate the associated loss of muscle strength and function (2, 3). Muscle loss begins in the fifth decade at an approximate rate of 1% per year for mass and 3% per year for strength (4, 5). As age advances, the losses accelerate, such that approximately 40% of muscle loss occurs during the eighth decade (6), reinforcing the striking decline observed by Rosenberg. The associations with poor mobility, increased dependency and mortality have sparked a wealth of research into musculoskeletal ageing over the ensuing decades with the current challenge to translate the emerging research findings into improved clinical care for older people.
Alongside ageing muscle, periods of immobility can lead to muscle atrophy, alterations to muscle metabolism and reduced muscle function across all ages (7, 8). This may be particularly detrimental to older people with sarcopenia as they start from a position of lower muscle mass and quality, compared to younger individuals (3, 5). Sarcopenia is proposed to contribute to the vulnerability that characterises physical frailty, with both conditions part of a self-perpetuating cycle that increases an individual’s susceptibility to the risks of acute muscle loss and negative metabolic health changes when that individual becomes physically inactive (9). This, in turn, makes rehabilitation more difficult and contributes to poor outcomes (10).
“Unfortunately, there are occasions where immobility is unavoidable such as the therapeutic immobilisation of, and restricted or non-weight bearing through, an affected limb for 6-8 weeks required to heal many common fragility factures. Little is known about the clinical characteristics of older people who sustain such injuries, but many, especially those with frailty, are discharged from acute hospitals to care homes, and exposed to further risks of immobility.” Dr Eleanor Lunt
The impact of immobilisation on the decline in their skeletal muscle mass, quality and function is also unknown. It is presumed these patients experience significant loss of muscle during the non-weight bearing period, influencing their subsequent physical functioning and clinical outcomes.
This study aims to follow 60 participants aged ≥70 years admitted to hospital with an acute non-weight bearing fracture. Measures of muscle strength (handgrip and knee extension), body composition (BIA) and muscle thickness (ultrasound) will occur longitudinally to detect muscle decline during the 6 weeks of immobility and at 4 months to look for recovery after physiotherapy. Clinical outcomes, dependency levels and frailty scores will also be recorded. A sub-group of the participants (n=20) will additionally undergo “deep phenotype” measures to characterise the level of muscle loss and behaviour using more detailed metabolic and molecular measurements at the whole-body and muscle levels. The research aims to guide further translational research targeting the ill-understood physiology of the musculoskeletal system in sarcopenia and frailty.
Dr Eleanor Lunt – PhD student
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