The Geelong Osteoporosis Study (GOS) suggests that current operational definitions for sarcopenia have overlooked assessment problems for older people with symptoms of depression.
The term sarcopenia originally meant ‘poverty of flesh’ and was synonymous with severe and generalised muscle wasting that can occur in older people.
Sarcopenia, which affects approximately 10% of older adults globally, contributes to falls, fractures, prolonged hospitalisation, loss of independence and early death.
The Geelong Osteoporosis Study (GOS), which I lead, is an established population-based cohort study as part of the program of research in Deakin’s Institute for Mental and Physical Health and Clinical Translation (IMPACT) at Barwon Health.
The GOS is unique in Australia in that it follows large, randomly selected groups of over 3200 adults, drawn from a wide range of socio-demographic backgrounds in Geelong and surrounding regions.
The study was originally established to investigate the epidemiology of osteoporosis and identify risk factors for fractures. It has subsequently expanded to also examine other aspects of musculoskeletal conditions and their interplay with psychological health.
Diagnosing sarcopenia
Sarcopenia was officially recognised as a disease entity in 2016, when the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code M62.84 was assigned.
While there is currently no internationally agreed way of defining sarcopenia, there has been a swell of support to change the way that the condition is diagnosed.
There has been a shift in focus away from loss of muscle mass to loss of muscle function. This is because poor muscle function predicts many adverse health outcomes that become apparent in older age.
So measures of muscle function, which include handgrip strength and walking speed, are prominent tests for identifying sarcopenia.
In their recent assessment phase, our GOS participants underwent clinical tests that included measures of handgrip strength to assess muscle strength, and a “Timed Up-and-Go” (TUG) test to assess walking speed and balance.
The handgrip test requires the participant to squeeze a hand-held dynamometer as hard as possible, separately with each hand, so the maximum value of repeated trials can be recorded.
In the TUG test, participants are asked to stand from a chair, walk a measured distance of 3 metres, turn around, return to the chair and sit down again. The time taken for this test is measured.
The study also looked at the effects of psychological wellbeing when undergoing these clinical tests.
Our data showed that women with depressive symptoms had lower measures in tests of handgrip strength and TUG than their peers who did not have depressive symptoms.
Muscle-mood connection
We know that physical and mental ill-health can be linked via destructive processes, including oxidative stress, inflammatory pathways and metabolic imbalances.
Other factors involved in the muscle-mood connection include stress-induced raised levels of cortisol – which has a potent effect on the breakdown of proteins in skeletal muscle – and disruption of the tryptophan degradation pathway – which lowers tryptophan and serotonin levels and impairs neuromuscular function, weakening muscle strength and reducing walking speed.
Furthermore, shared lifestyle factors such as physical inactivity, poor nutrition and smoking affect both muscle health and mood.
Meaningful measures of muscle strength and performance, which rely on participant effort, are subject to participant fatigue, pain, motivation and purpose.
The study also found that participants with depressive symptoms were more likely to report feelings of tiredness and low energy, perceived pain and insomnia. These problems exacerbate difficulties in assessing muscle function using current clinical testing procedures.
This study has identified the importance of considering psychological wellbeing when setting criteria for diagnosing sarcopenia.
We recommend that operational definitions should consider an individual’s mood at the time of muscle function evaluation.
In the future, inclusion of depression in the diagnostic criteria for sarcopenia will likely improve the identification and management of the disease.
Curious? Discover more about this work from the Geelong Osteoporosis Study.
Julie Pasco is a Professor of Epidemiology in Deakin’s Institute for Mental and Physical Health and Clinical Translation (IMPACT) Institute at Barwon Health, where she heads the Epi-Centre for Healthy Ageing.
Professor Pasco has received speaker fees from Amgen, Eli Lilly and Sanofi-Aventis and funding from the NHMRC, MRFF, Barwon Health, Deakin University, the BUPA Foundation, Osteoporosis Australia, Australia and New Zealand Bone and Mineral Society, the Geelong Community Foundation, the Western Alliance, Amgen and the Norman Beischer Foundation.
