The term ‘sarcopenia’ comes from ‘sarco-’, the Greek word for ‘flesh’ (muscle), and ‘-penia’ which denotes ‘deficiency’. The original definition reflected this as ‘the degenerative loss of skeletal muscle mass that accompanies ageing (0.5–1% loss per year after the age of 25)’ (Cruz-Jentoft et al., 2010). However over time, the definition has been altered and used to suit clinical practice needs, linking the term with physical outcomes, to the point that it no longer represents it’s etymological origin. For example, the European Working Group on Sarcopenia in Older People (EWGSOP) broadened the definition of sarcopenia to include loss of muscle strength or low functional performance in addition to low muscle mass (Cruz-Jentoft et al., 2010). This broad add-on reflects mobility or motor impairment and is not dissimilar to the multidimensional construct of frailty, widely used in clinical practice (Bauer & Sieber, 2008).
Despite a large body of literature, there is no consensus on the definition of sarcopenia, no standardised assessments, and no validation of cut-off values. This presents a substantial impediment to the clinical use of the term sarcopenia. This likely explains the large variation in sarcopenia prevalence reported across studies of older people: between 10 and 90% (Batsis et al., 2013; Patil et al., 2013).
Using a sample of 419 community-living older people (average age 81), we compared 7 different definitions of sacropenia for their ability to predict important functional and health-related outcomes. These included 4 definitions based on skeletal muscle mass, two based on strength measures and the combination muscle mass and function definition of EWGSOP described above. Participants completed assessments of body composition (including muscle mass, using dual-energy X-ray absorptiometry), strength, balance, mobility and disability, and reported falls monthly for one year.
WHAT DID WE FIND?
The four skeletal mass-based definitions varied considerably in classifying participants as sarcopenic, ranging from 14 to 73%. Their predictive accuracy for functional and health outcomes was no better than the simple knee extension strength-based definition; i.e. weaker participants performed poorly in tests of leaning balance, stepping reaction time, gait speed and mobility, had higher physiological fall risk scores, and were 43% more likely to fall at home than their stronger counterparts.
SIGNIFICANCE AND IMPLICATIONS
A simple lower limb strength assessment was at least as effective in predicting balance, functional mobility and falls in older people as the more expensive and time-consuming muscle mass-based measures. These findings imply that functional terms such as muscle weakness or motor impairment are preferable to sarcopenia for clinical use. To predict health and functional performance, a clinician could simply administer a quick and simple muscle strength test.
Menant JC, Weber F, Lo J, Sturnieks DL, Close JC, Sachdev PS, Brodaty H, Lord SR. (2016). Strength measures are better than muscle mass measures in predicting health-related outcomes in older people: time to abandon the term sarcopenia? Osteoporos Int, Epub ahead of print. doi: 10.1007/s00198-016-3691-7.
Batsis JA, Barre LK, Mackenzie TA, Pratt SI, Lopez-Jimenez F, Bartels SJ. (2013). Variation in the prevalence of sarcopenia and sarcopenic obesity in older adults associated with different research definitions: dual-energy X-ray absorptiometry data from the National Health and Nutrition Examination Survey 1999–2004. J Am Geriatr Soc, 61, 974–980. doi: 10.1111/jgs.12260.
Bauer JM, Sieber CC. (2008). Sarcopenia and frailty: a clinician’s controversial point of view. Exp Gerontol 43, 674–678. doi: 10.1016/j.exger.2008.03.007.
Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F et al. (2010). Sarcopenia: European consensus on definition and diagnosis: report of the European Working Group on Sarcopenia in Older People. Age Ageing 39, 412–423. doi: 10.1093/ageing/afq034.
Patil R, Uusi-Rasi K, Pasanen M, Kannus P, Karinkanta S, Sievanen H. (2013). Sarcopenia and osteopenia among 70-80-year old home-dwelling Finnish women: prevalence and association with functional performance. Osteoporos Int 24, 787–796. doi: 10.1007/s00198-012-2046-2.
AUTHORS OF BLOG POST
Daina Sturnieks and Jasmine Menant