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Sarcopenia - Definition and diagnostic measures

By Mike Edgar & Ben Csiernik

Most individuals nowadays have heard the term ‘osteoporosis’ which typically means the loss of bone quality associated with aging. Although aging as an experience in itself does not cause osteoporosis, the co-morbid factors associated with aging predispose the elderly to it. A lesser known condition, sarcopenia, can be thought of in the same terms as osteoporosis, but relating to muscle tissue. Both of these conditions are not mutually exclusive and their concurrent onset is common and noted in the literature as osteosarcopenia. Sarcopenia was first defined by Rosenberg in 1989 as “the poverty or deficiency of flesh” (1). More recently, the European Working Group on Sarcopenia in Older People (EWGSOP) developed a practical clinical definition and consensus diagnostic criteria for age-related sarcopenia (2). They described it as, ‘the presence of both low muscle mass and low muscle function in elderly individuals (2).

An important distinction needs to be made between crude measurements of muscle girth versus more accurate measures of muscle size and quality. The photos provided gives a cross-section of a sedentary, 70-year-old individual compared to an active, 70-year-old individual. Although the cross-sectional area shown for both images is quite similar, the gross disproportion of adipose tissues and fatty infiltration within the muscle tissue is quite evident. The effects of this for the individual relate to deficiencies in activities of daily living, increased mortality in hospitalized patients, greater depressive symptoms and increased rates of adverse outcomes like falls and reduced mobility to name a few (3). From a societal perspective, it has been associated with greater costs due to increased hospital stay duration and increased non-elective readmission to the hospital during a six month follow-up period (3). Overall, it has been found to have far-reaching effects from an individual to societal level with prevalence rate estimates of sarcopenia in community-dwelling older individuals ranging between 3% and 52% (4-5). As noted from its definition, sarcopenia can be described through both functional and structural terms and therefore, the measures associated with its diagnosis are varied in their approach but apparent in their importance.


A comprehensive systematic review by Mijnarends et al. 2013 compared several muscle mass measures, functional outcomes and strength measures compared to the gold standard of magnetic resonance imaging (MRI). Through this review, it was found that imaging techniques like computed tomography (CT) and Dual-energy X-ray absorptiometry (DEXA) offered a valid means for the diagnosis of sarcopenia, but their utility in a clinical setting may be limited (3). That being said, they also found several strength and functional outcomes that can offer an appropriate means to its diagnosis. For example, low scores in: handheld dynamometry (a hand grip strength test), gait speed, and the short physical performance battery (SPPB) which provide a valid and reliable measurement of muscle strength and physical performance are all potential indicators of sarcopenia (3). Although functional and strength measures of sarcopenia appear to have better utilization in a clinical setting, direct measures of muscle mass are typically limited. That being said, bioelectrical impedance analysis (BIA) may offer an option for diagnostic purposes (3). BIA measures lean body mass through the use of electrical conductance to determine the resistance to flow as the current passes through the body (3). This provides an estimate of body composition using specific equations programmed into the device allowing for the detection of sarcopenia (3). Mijnarends et al. 2013 found bioelectrical impedance (BIA) to have high concurrent validity although reliability was varied due to factors like hydration status (3).

A second systematic review by Miller et al. investigated the reliability and validity of various tools for this same condition (6). Two tools, the Short Portable Sarcopenia Measure (SPSM) and the SARC-F (Strength, Assistance with walking, Rise from a chair, Climb stairs, and Falls) were considered effective for the diagnosis of sarcopenia (6). Moreso, a systematic review by Nijholt et al. in 2017 investigated the use of ultrasound for the assessment of sarcopenia compared to the gold standard or DEXA analysis. They found ultrasound to be reliable and valid for the assessment of muscle size in older adults (7). Even though the utility of these measures seems promising, we need to remember that variability does exist in different populations as noted by Dodds et al. in 2016 who investigated differences in grip strength by world region. They found the average grip strength measurements were substantially lower in developing countries compared with the developed world regions (8). This review highlighted that the consensus definitions of sarcopenia and frailty may need different cut-off points for grip strength for different geographical regions. Although it may be speculation, I feel this recommendation could apply to the majority of measures described in this article.

Now that you understand the basis and effects of sarcopenia and measurement tools associated with it, you can begin to implement these tools in a variety of settings. The first and most convenient step may be to use the SARC-F form, which is a simple 5 question rating questionnaire. A score of 4 or greater is predictive of sarcopenia and poor outcomes in daily activities (9).



Following the SARC-F (in the absence of advanced imaging), the best ways to test for “probable” sarcopenia are grip strength or knee extension strength (10). Once you have tested grip strength or knee extensor strength, the “severity” of sarcopenia can further be assessed using the chair stand test (5 repetitions as quickly as possible), the Short Personal Performance Battery, the Timed ‘Get Up and Go’ test, or the 400m walk test. The cut-off values for all of these diagnostic tests are listed below as demonstrated by the updated EWSOP (10).


Knee Extension Strength Cut-Offs 1 - Men - 90Nm and Women - 60Nm (11)

Overall, there are a few main points I want to highlight about sarcopenia. Firstly, that as a condition it is generally not as well-known as its counterpart osteoporosis, but arguably it is just as important to be aware of. Secondly, it has a number of wide-ranging effects related to the individual-level and population-level. Thirdly, there is a high degree of variability in measures for the diagnosis of sarcopenia but based on access, convenience and priority, the method best suited to your situation can be found and implemented. On a final note, even though conservative interventions associated with the treatment of sarcopenia will be discussed in later articles, this condition does highlight the importance of proper nutrition and exercise for both its prevention and management.



References:


  1. Fox B, Henwood T, Schaap L, Bruyère O, Reginster JY, Beaudart C, Buckinx F, Roberts H, Cooper C, Cherubini A, dellʼAquilla G, Maggio M, Volpato S. Adherence to a standardized protocol for measuring grip strength and appropriate cut-off values in adults over 65 years with sarcopenia: a systematic review protocol. JBI Database System Rev Implement Rep. 2015 Oct;13(10):50-9. Doi: 10.11124/jbisrir-2015-2256. PubMed [citation] PMID: 26571282

  2. Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F, Martin FC, Michel JP, Rolland Y, Schneider SM, Topinková E. Sarcopenia: European consensus on definition and diagnosisReport of the European Working Group on Sarcopenia in Older PeopleA. J. Cruz-Gentoft et al. Age and ageing. 2010 Jul 1;39(4):412-23.

  3. Mijnarends DM, Meijers JM, Halfens RJ, ter Borg S, Luiking YC, Verlaan S, Schoberer D, Jentoft AJ, van Loon LJ, Schols JM. Validity and reliability of tools to measure muscle mass, strength, and physical performance in community-dwelling older people: a systematic review. Journal of the American Medical Directors Association. 2013 Mar 1;14(3):170-8.

  4. Fielding RA, Vellas B, Evans WJ, Bhasin S, Morley JE, Newman AB, van Kan GA, Andrieu S, Bauer J, Breuille D, Cederholm T. Sarcopenia: an undiagnosed condition in older adults. Current consensus definition: prevalence, etiology, and consequences. International working group on sarcopenia. Journal of the American Medical Directors Association. 2011 May 1;12(4):249-56.

  5. Mijnarends DM, Meijers JM, Halfens RJ, ter Borg S, Luiking YC, Verlaan S, Schoberer D, Jentoft AJ, van Loon LJ, Schols JM. Validity and reliability of tools to measure muscle mass, strength, and physical performance in community-dwelling older people: a systematic review. Journal of the American Medical Directors Association. 2013 Mar 1;14(3):170-8.

  6. Miller J, Wells L, Nwulu U, Currow D, Johnson MJ, Skipworth RJE. Validated screening tools for the assessment of cachexia, sarcopenia, and malnutrition: a systematic review. Am J Clin Nutr. 2018 Dec 1;108(6):1196-1208. doi:10.1093/ajcn/nqy244. PubMed [citation] PMID: 30541096

  7. Nijholt W, Scafoglieri A, Jager-Wittenaar H, Hobbelen JSM, van der Schans CP. The reliability and validity of ultrasound to quantify muscles in older adults: a systematic review. J Cachexia Sarcopenia Muscle. 2017 Oct;8(5):702-712. Doi: 10.1002/jcsm.12210. Epub 2017 Jul 12. Review. PubMed [citation] PMID: 28703496, PMCID: PMC5659048

  8. Dodds RM, Syddall HE, Cooper R, Kuh D, Cooper C, Sayer AA. Global variation in grip strength: a systematic review and meta-analysis of normative data. Age Ageing. 2016 Mar;45(2):209-16. doi: 10.1093/ageing/afv192. Epub 2016 Jan 19. Review. PubMed [citation] PMID: 26790455, PMCID: PMC4776623

  9. Malmstrom TK, Morley JE. SARC-F: a simple questionnaire to rapidly diagnose sarcopenia. Journal of the American Medical Directors Association. 2013 Aug 1;14(8):531-2.

  10. Cruz-Jentoft AJ, Bahat G, Bauer J, Boirie Y, Bruyère O, Cederholm T, Cooper C, Landi F, Rolland Y, Sayer AA, Schneider SM. Sarcopenia: revised European consensus on definition and diagnosis. Age and ageing. 2019 Jan 1;48(1):16-31.

  11. Newman AB, Kupelian V, Visser M, Simonsick EM, Goodpaster BH, Kritchevsky SB, Tylavsky FA, Rubin SM, Harris TB. Strength, but not muscle mass, is associated with mortality in the health, aging and body composition study cohort. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 2006 Jan 1;61(1):72-7.