- Email: [email protected]
Sarcopenia: A useful paradigm for physical frailty
European Geriatric Medicine 4 (2013) 102–105
Available online at
www.sciencedirect.com
Controversies in geriatric medicine
Sarcopenia: A useful paradigm for physical frailty A.J. Cruz-Jentoft a,*, J.-P. Michel b a b
Servicio de Geriatrı´a, Hospital Universitario Ramo´n y Cajal, Madrid, Spain Geneva University, Geneva, Switzerland
A R T I C L E I N F O
A B S T R A C T
Article history: Received 31 October 2012 Accepted 25 February 2013 Available online 8 April 2013
The concepts and definitions of frailty and sarcopenia are being actively revised in recent times. The most popular present definitions of sarcopenia and physical frailty share many common points. Both sarcopenia and frailty may be best understood when considered as geriatric syndromes. Geriatric syndromes are relevant because they are usually the presenting manifestation of multiple underlying diseases and conditions; they cause morbidity by themselves; and are only treatable when a multidimensional approach is used. Frailty can be well understood as a geriatric syndrome. The risk of frailty increases with age and with the accumulated effects of multiple conditions and predisposing factors, and subjects identified as frail have impaired outcomes. Sarcopenia is also best understood as a geriatric syndrome. Frailty is a complex problem that includes physical, functional, mental and social aspects. Physical frailty has close links to muscle function, and therefore to the new definitions of sarcopenia. Many of the adverse outcomes of frailty are probably mediated by sarcopenia. Sarcopenia can be considered as being a key pathway between frailty and disability. Although frailty affects both musculoskeletal and non-musculoskeletal systems, sarcopenia constitutes one of the main components of the clinical frailty syndrome. The concept of sarcopenia being closer to the musculoskeletal system (the organ system with the function of mobility), we propose that sarcopenia, using recent definitions and considered as a geriatric syndrome, is a more useful paradigm and one that may be easier to put into operational definitions than physical frailty for clinical prevention, diagnosis and intervention. Diagnostic criteria for sarcopenia may be used to measure physical frailty in research and practice. ß 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved.
Keywords: Sarcopenia Frailty Physical frailty Undernutrition Diagnostic criteria
1. Introduction The concepts and definitions of frailty and sarcopenia are being actively revised in recent times [1–3]. Initial definitions of frailty considered it as a synonymous of disability, multimorbidity or extreme old age, being only a subjective perception by the clinician [4]. During the last decade the concept of frailty started to approach some consensus: frailty is a biological syndrome of decreased reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems and causing vulnerability to adverse outcomes [5]. However, this concept has proved elusive when it is brought to clinical practice. Frailty is a complex and multidimensional construct, which explains the problems involved in its working definition and operationalization in clinical research and practice [6]. Current thinking is that frailty cannot be limited to a physical paradigm; psychological, cognitive, emotional, social and spiritual factors
* Corresponding author. Servicio de Geriatrı´a, Hospital Universitario Ramo´n y Cajal, Ctra. Colmenar, km 9,1, 28034 Madrid, Spain. Tel.: +34 91 33 68 431. E-mail addresses: [email protected], [email protected] (A.J. Cruz-Jentoft).
contribute to frailty and need to be taken into account in its definition [1]. Research on physical frailty is far more advanced than research on other aspects of frailty. A phenotypical approach to physical frailty has been introduced in clinical practice [5], although it has not shown full success in the prediction of outcomes [7,8]. An alternative model of accumulation of deficits has also been used [9,10]. None of these approaches seem to yield similar results in clinical practice [11], which is again confusing to our present understanding of physical frailty. What do these indicators of frailty really measure? Physical frailty is strongly linked to muscle mass and function. In 1988, Irwin H. Rosenberg stated that ‘‘over the decades of life, there is probably no decline in structure and function more dramatic than the decline in lean body mass or muscle mass’’ [12]. He postulated that this decline has a negative impact on ambulation, mobility, breathing, energy intake, overall nutrient intake and status and independence. He suggested giving it a name: sarcopenia. The definition of sarcopenia has also been evolving since it was named, starting from muscle mass and moving toward muscle strength and function, physical performance and impaired outcomes [2,13,14]. One of the most recent
1878-7649/$ – see front matter ß 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved. http://dx.doi.org/10.1016/j.eurger.2013.02.009
A.J. Cruz-Jentoft, J.-P. Michel / European Geriatric Medicine 4 (2013) 102–105
definitions states that sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes, such as physical disability, poor quality of life and death [14]. Many would argue that the whole picture depicted here for sarcopenia is not far from the current phenotypic definition of frailty. A careful examination of the most popular present definitions of sarcopenia and physical frailty shows that they share many common points. For instance, three out of five elements of Fried’s phenotypical definition of physical frailty (shrinking, weakness, slowness) [5] are part of the EWGSOP definition of sarcopenia [14]. However, from a physiological and clinical perspective, sarcopenia is closer to an organ function (skeletal muscle) than frailty, and may be easier to apply in clinical practice. Drug regulatory agencies consider frailty a problematic indication for drug approval [15] and may find sarcopenia (broadly viewed as ‘‘muscle insufficiency’’, which is closer to most organs and system disease pathways) a simpler construct. In this paper, we will review how the concept of geriatric syndromes has changed, we will explore some syndromic approaches to frailty and sarcopenia, and we will argue that sarcopenia is the major determinant of physical frailty. We will, thus, propose that sarcopenia is a useful paradigm for physical frailty.
2. The evolving concept of geriatric syndromes One of the problems that are complicating the development and validation of the concepts of frailty and sarcopenia is that both need to be distinguished from normal age-related changes and from other age-related diseases and conditions. In fact, recent literature shows that both sarcopenia and frailty may be best understood when considered as geriatric syndromes [16–18]. The term ‘‘geriatric syndrome’’ has been commonly used in the geriatric literature for decades to define complex clinical conditions that are common in older persons and do not fit into discrete disease categories, such delirium, dementia or gait disorders. The concept of geriatric syndromes is usually well understood by any professional working in geriatric medicine, and most geriatric textbooks include a series of chapters on their diagnosis and management. However, there are some discrepancies in the understanding of such syndromes, which may be related with how sparse the literature is in conceptualizing geriatric syndromes [19,20]. Geriatric syndromes correspond to observable characteristics at the physical, morphologic and biochemical levels of an individual as determined by the genotype and the environment [21]. They capture clinical conditions in older persons that do not fit into disease categories, but are highly prevalent in old age, multifactorial, associated with multiple co-morbidities and poor outcomes, such as increased disabilities and decreased quality of life [22]. The conceptual understanding of a geriatric problem as a geriatric syndrome has been shown to be feasible and useful in predicting outcomes [23]. Geriatric syndromes have been defined as health conditions common in older persons that result from the accumulated effect of multiple predisposing factors and that may be precipitated by an acute insult. Geriatric syndromes are relevant because they are usually the presenting manifestation of multiple underlying diseases and conditions; they cause morbidity by themselves; and are only treatable when a multidimensional approach is used. Screening for geriatric syndromes seems to be more effective than using medical diagnosis in identifying frail older subjects at risk for mortality and nursing home utilization [24,25].
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3. A syndromic approach to sarcopenia and frailty Being said that, frailty can be well understood as a geriatric syndrome. Frailty, and even isolated physical frailty, does not seem to fit into a single disease category, or to be only usual ageing. In specific life environments/conditions, it can be the consequence of a single disease and of multimorbid conditions [22]. It can be identified or defined by observing or measuring different clinical features, being the clinical manifestation of multiple underlying diseases and complex conditions. The risk of frailty increases with age and with the accumulated effects of multiple conditions and predisposing factors, and subjects identified as frail have impaired outcomes (function, morbidity, mortality, costs). Thus, it fulfills most of the characteristics that define other geriatric syndromes (i.e. delirium, falls). Frailty seems to be interlinked with other geriatric syndromes and with functional dependence, which is again consistent with our understanding of other geriatric syndromes [26]. However, frailty is an extremely complex paradigm. Research on the underlying biologic basis for frailty by studying basic homeostatic pathways and mechanisms has not yet yielded many relevant results, and these pathways seem to be extremely intricate, as shown by the growing number and complexity of the ‘‘cycles of frailty’’ published in recent years [27,28]. Moreover, the link between frailty and ageing is extremely difficult to apprehend [6]. We have also showed recently that sarcopenia is best understood as a geriatric syndrome [16]. This syndromic view has been acknowledged by the EWGSOP definition (‘‘sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength or function with a risk of adverse outcomes, such as physical disability, poor quality of life and death’’) [13,14]. Nowadays, discussions are mostly focused on a better understanding of the physiopathology, the early recognition of risk factors, an integrative approach on clinical presentations (from presarcopenia to severe sarcopenia or sarcopenia with mobility disorders), complications and prevention treatment or reversibility of the loss of skeletal muscle mass, strength and function. Muscle function cannot be understood without bones. As research on osteoporosis and fractures is more advanced than research in sarcopenia and frailty [29], it is not surprising that there is a recent tendency to explore their functional links [30]. Even the term sarco-osteoporosis has been coined [31]. Sarcopenia and osteoporosis seem to be additive in predicting physical frailty [32]. Thus, studies of musculoskeletal frailty[33] are starting to be published. 4. Sarcopenia, the major determinant of physical frailty Older definitions of sarcopenia, based only on absolute or relative muscle mass, are losing relevance, as it is now clear that muscle mass, strength and function do not run parallel. The concept of frailty developed in this arena, pointing out that functional aspects were more relevantly linked to relevant health outcomes than muscle mass [34]. However, new definitions of sarcopenia have moved away from the ‘‘muscle mass only’’ concept to include muscle function and physical performance. As mentioned before, physical frailty has close links to muscle function, and therefore to the new concept and definition of sarcopenia [35,36]. The consequences of sarcopenia are mainly impaired mobility, disability for basic activities of daily living, and increased mortality. Sarcopenia is also associated with impairments in other physiological functions, including glucose regulation, hormone production, cellular communication and protein storage and turnover. In fact, many of the adverse outcomes of frailty are probably mediated by sarcopenia.
104
A.J. Cruz-Jentoft, J.-P. Michel / European Geriatric Medicine 4 (2013) 102–105
Fig. 1. A conceptual model for sarcopenia and frailty.
Disclosure of interest The authors have not supplied their declaration of conflict of interest. References [1] Rodriguez-Manas L, Feart C, Mann G, et al. Searching for an operational definition of frailty: a delphi method based consensus statement. The Frailty Operative Definition-Consensus Conference Project. J Gerontol A Biol Sci Med Sci 2012.
[2] Cederholm TE, Bauer JM, Boirie Y, et al. Toward a definition of sarcopenia. Clin Geriatr Med 2011;27:341–53. [3] Morley JE, Cruz-Jentoft AJ. Definitions of sarcopenia. In: Cruz-Jentoft AJ, Morley JE, editors. Sarcopenia. Chichester: Wiley-Blackwell; 2012. p. 8–19. [4] Hamerman D. Toward an understanding of frailty. Ann Intern Med 1999;130:945–50. [5] Fried LP, Tangen CM, Walston J, et al. Frailty in older adults: evidence for a phenotype. J Gerontol A Biol Sci Med Sci 2001;56:M146–56. [6] Bergman H, Ferrucci L, Guralnik J, et al. Frailty: an emerging research and clinical paradigm–issues and controversies. J Gerontol A Biol Sci Med Sci 2007;62:731–7. [7] Pijpers E, Ferreira I, Stehouwer CD, et al. The frailty dilemma. Review of the predictive accuracy of major frailty scores. Eur J Intern Med 2012;23:118–23. [8] Sternberg SA, Wershof SA, Karunananthan S, et al. The identification of frailty: a systematic literature review. J Am Geriatr Soc 2011;59:2129–38. [9] Rockwood K, Andrew M, Mitnitski A. A comparison of two approaches to measuring frailty in elderly people. J Gerontol A Biol Sci Med Sci 2007;62:738– 43. [10] Mitnitski AB, Mogilner AJ, MacKnight C, et al. The mortality rate as a function of accumulated deficits in a frailty index. Mech Ageing Dev 2002;123:1457– 60. [11] Woo J, Leung J, Morley JE. Comparison of frailty indicators based on clinical phenotype and the multiple deficit approach in predicting mortality and physical limitation. J Am Geriatr Soc 2012;60:1478–86. [12] Rosenberg IH. Summary comments: epidemiological and methodological problems in determining nutritional status of older persons. Clin Nutr 1989;50:1231–3. [13] Morley JE, Abbatecola AM, Argiles JM, et al. Sarcopenia with limited mobility: an international consensus. J Am Med Dir Assoc 2011;12:403–9. [14] Cruz-Jentoft AJ, Baeyens JP, Bauer JM, et al. Sarcopenia: European consensus on definition and diagnosis: report of the European working group on sarcopenia in older people. Age Ageing 2010;39:412–23. [15] Working Group on functional outcome measures for clinical trials. Indications, labeling, and outcome assessment for drugs aimed at improving functional status in older persons: conversations between aging researchers and FDA regulators. J Gerontol A Biol Sci Med Sci 2009;64A:487–91. ˜ E, et al. Understanding sarcopenia as a [16] Cruz-Jentoft AJ, Landi F, TopinkovA geriatric syndrome. Curr Opin Clin Nutr Metab Care 2010;13:1–7. [17] Ruiz M, Cefalu C, Reske T. Frailty syndrome in geriatric medicine. Am J Med Sci 2012. [18] Clegg A, Young J. The frailty syndrome. Clin Med 2011;11:72–5. [19] Olde Rikkert MG, Rigaud AS, van Hoeyweghen RJ, et al. Geriatric syndromes: medical misnomer or progress in geriatrics? Neth J Med 2003;61:83–7. [20] Flacker JM. What is a geriatric syndrome anyway? J Am Geriatr Soc 2003;51:574–6. [21] Inouye SK, Studenski S, Tinetti ME, et al. Geriatric syndromes: clinical, research, and policy implications of a core geriatric concept. J Am Geriatr Soc 2007;55:780–91. !
Sarcopenic subjects show increased vulnerability, which is a dynamic process of negative adaptation in the face of adversity or external stressors. Sarcopenia plays a crucial etiological role in the frailty process itself, being also a key player of its latent phase and explaining numerous phenomenologies of the frailty status. Although frailty is a more complex problem that includes physical, functional, mental and social aspects, in our view sarcopenia can be considered as being a key pathway between frailty and disability (Fig. 1). There is an urgent need to obtain an operational definition of musculoskeletal health that can be used for prevention and therapy [37] and there is much confusion between these terms [38]. A better conceptualization of sarcopenia and frailty seems to be extremely relevant for the future development of geriatric medicine in its quest for preventing and fighting disability [39]. Although frailty affects both musculoskeletal and non-musculoskeletal systems, sarcopenia constitutes one of the main components of the clinical frailty syndrome [33]. Being the concept of sarcopenia closer to the musculoskeletal system (the organ system with the function of mobility), we propose that sarcopenia, using recent definitions and considered as a geriatric syndrome, is a more useful paradigm and one that may be easier to put into operational definitions than physical frailty for clinical prevention, diagnosis and intervention. This may also bring a better understanding of the physical aspects of frailty within a broader concept of frailty that includes all aspects of human life.
A.J. Cruz-Jentoft, J.-P. Michel / European Geriatric Medicine 4 (2013) 102–105 [22] Sanders JL, Boudreau RM, Fried LP, et al. Measurement of organ structure and function enhances understanding of the physiological basis of frailty: the Cardiovascular Health Study. J Am Geriatr Soc 2011;59:1581–8. [23] Kane RL, Shamliyan T, Talley K, et al. The association between geriatric syndromes and survival. J Am Geriatr Soc 2012;60:896–904. [24] Drame M, Fierobe F, Lang PO, et al. Predictors of institution admission in the year following acute hospitalisation of elderly people. J Nutr Health Aging 2011;15:399–403. [25] Bilotta C, Nicolini P, Case A, et al. Frailty syndrome diagnosed according to the study of osteoporotic fractures (SOF) criteria and adverse health outcomes among community-dwelling older outpatients in Italy. A one-year prospective cohort study. Arch Gerontol Geriatr 2012;54:e23–8. [26] Tinetti ME, Inouye SK, Gill TM, et al. Shared risk factors for falls, incontinence, and functional dependence. Unifying the approach to geriatric syndromes. JAMA 1995;273:1348–53. [27] Marzetti E, Calvani R, Bernabei R, et al. Apoptosis in skeletal myocytes: a potential target for interventions against sarcopenia and physical frailty - a mini-review. Gerontology 2012;58:99–106. [28] Sanchis-Gomar F, Gomez-Cabrera MC, Vina J. The loss of muscle mass and sarcopenia: non hormonal intervention. Exp Gerontol 2011;46:967–9. [29] Bijlsma AY, Meskers CG, Westendorp RG, et al. Chronology of age-related disease definitions: osteoporosis and sarcopenia. Ageing Res Rev 2012;11:320–4. [30] Matthews GD, Huang CL, Sun L, et al. Translational musculoskeletal science: is sarcopenia the next clinical target after osteoporosis? Ann N Y Acad Sci 2011;1237:95–105.
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[31] Buehring B, Krueger D, Binkley N. Effect of including historical height and radius BMD measurement on sarco-osteoporosis prevalence. J Cachexia Sarcopenia Muscle 2012. [32] Frisoli Jr A, Chaves PH, Ingham SJ, et al. Severe osteopenia and osteoporosis, sarcopenia, and frailty status in community-dwelling older women: results from the Women’s Health and Aging Study (WHAS) II. Bone 2011;48:952–7. [33] Gielen E, Verschueren S, O’Neill TW, et al. Musculoskeletal frailty: a geriatric syndrome at the core of fracture occurrence in older age. Calcif Tissue Int 2012;91:161–77. [34] Bauer JM, Sieber CC. Sarcopenia and frailty: a clinician’s controversial point of view. Exp Gerontol 2008;43:674–8. [35] Vanitallie TB. Frailty in the elderly: contributions of sarcopenia and visceral protein depletion. Metabolism 2003;52:22–6. [36] Evans WJ, Paolisso G, Abbatecola AM, et al. Frailty and muscle metabolism dysregulation in the elderly. Biogerontology 2010;11:527–36. [37] Cooper C, Dere W, Evans W, et al. Frailty and sarcopenia: definitions and outcome parameters. Osteoporos Int 2012;23:1839–48. [38] Jeejeebhoy KN. Malnutrition, fatigue, frailty, vulnerability, sarcopenia and cachexia: overlap of clinical features. Curr Opin Clin Nutr Metab Care 2012;15:213–9. [39] Vellas B, Cestac P, Moley JE. Editorial: implementing frailty into clinical practice: we cannot wait. J Nutr Health Aging 2012;16:599–600.
Available online at
www.sciencedirect.com
Controversies in geriatric medicine
Sarcopenia: A useful paradigm for physical frailty A.J. Cruz-Jentoft a,*, J.-P. Michel b a b
Servicio de Geriatrı´a, Hospital Universitario Ramo´n y Cajal, Madrid, Spain Geneva University, Geneva, Switzerland
A R T I C L E I N F O
A B S T R A C T
Article history: Received 31 October 2012 Accepted 25 February 2013 Available online 8 April 2013
The concepts and definitions of frailty and sarcopenia are being actively revised in recent times. The most popular present definitions of sarcopenia and physical frailty share many common points. Both sarcopenia and frailty may be best understood when considered as geriatric syndromes. Geriatric syndromes are relevant because they are usually the presenting manifestation of multiple underlying diseases and conditions; they cause morbidity by themselves; and are only treatable when a multidimensional approach is used. Frailty can be well understood as a geriatric syndrome. The risk of frailty increases with age and with the accumulated effects of multiple conditions and predisposing factors, and subjects identified as frail have impaired outcomes. Sarcopenia is also best understood as a geriatric syndrome. Frailty is a complex problem that includes physical, functional, mental and social aspects. Physical frailty has close links to muscle function, and therefore to the new definitions of sarcopenia. Many of the adverse outcomes of frailty are probably mediated by sarcopenia. Sarcopenia can be considered as being a key pathway between frailty and disability. Although frailty affects both musculoskeletal and non-musculoskeletal systems, sarcopenia constitutes one of the main components of the clinical frailty syndrome. The concept of sarcopenia being closer to the musculoskeletal system (the organ system with the function of mobility), we propose that sarcopenia, using recent definitions and considered as a geriatric syndrome, is a more useful paradigm and one that may be easier to put into operational definitions than physical frailty for clinical prevention, diagnosis and intervention. Diagnostic criteria for sarcopenia may be used to measure physical frailty in research and practice. ß 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved.
Keywords: Sarcopenia Frailty Physical frailty Undernutrition Diagnostic criteria
1. Introduction The concepts and definitions of frailty and sarcopenia are being actively revised in recent times [1–3]. Initial definitions of frailty considered it as a synonymous of disability, multimorbidity or extreme old age, being only a subjective perception by the clinician [4]. During the last decade the concept of frailty started to approach some consensus: frailty is a biological syndrome of decreased reserve and resistance to stressors, resulting from cumulative declines across multiple physiologic systems and causing vulnerability to adverse outcomes [5]. However, this concept has proved elusive when it is brought to clinical practice. Frailty is a complex and multidimensional construct, which explains the problems involved in its working definition and operationalization in clinical research and practice [6]. Current thinking is that frailty cannot be limited to a physical paradigm; psychological, cognitive, emotional, social and spiritual factors
* Corresponding author. Servicio de Geriatrı´a, Hospital Universitario Ramo´n y Cajal, Ctra. Colmenar, km 9,1, 28034 Madrid, Spain. Tel.: +34 91 33 68 431. E-mail addresses: [email protected], [email protected] (A.J. Cruz-Jentoft).
contribute to frailty and need to be taken into account in its definition [1]. Research on physical frailty is far more advanced than research on other aspects of frailty. A phenotypical approach to physical frailty has been introduced in clinical practice [5], although it has not shown full success in the prediction of outcomes [7,8]. An alternative model of accumulation of deficits has also been used [9,10]. None of these approaches seem to yield similar results in clinical practice [11], which is again confusing to our present understanding of physical frailty. What do these indicators of frailty really measure? Physical frailty is strongly linked to muscle mass and function. In 1988, Irwin H. Rosenberg stated that ‘‘over the decades of life, there is probably no decline in structure and function more dramatic than the decline in lean body mass or muscle mass’’ [12]. He postulated that this decline has a negative impact on ambulation, mobility, breathing, energy intake, overall nutrient intake and status and independence. He suggested giving it a name: sarcopenia. The definition of sarcopenia has also been evolving since it was named, starting from muscle mass and moving toward muscle strength and function, physical performance and impaired outcomes [2,13,14]. One of the most recent
1878-7649/$ – see front matter ß 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved. http://dx.doi.org/10.1016/j.eurger.2013.02.009
A.J. Cruz-Jentoft, J.-P. Michel / European Geriatric Medicine 4 (2013) 102–105
definitions states that sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes, such as physical disability, poor quality of life and death [14]. Many would argue that the whole picture depicted here for sarcopenia is not far from the current phenotypic definition of frailty. A careful examination of the most popular present definitions of sarcopenia and physical frailty shows that they share many common points. For instance, three out of five elements of Fried’s phenotypical definition of physical frailty (shrinking, weakness, slowness) [5] are part of the EWGSOP definition of sarcopenia [14]. However, from a physiological and clinical perspective, sarcopenia is closer to an organ function (skeletal muscle) than frailty, and may be easier to apply in clinical practice. Drug regulatory agencies consider frailty a problematic indication for drug approval [15] and may find sarcopenia (broadly viewed as ‘‘muscle insufficiency’’, which is closer to most organs and system disease pathways) a simpler construct. In this paper, we will review how the concept of geriatric syndromes has changed, we will explore some syndromic approaches to frailty and sarcopenia, and we will argue that sarcopenia is the major determinant of physical frailty. We will, thus, propose that sarcopenia is a useful paradigm for physical frailty.
2. The evolving concept of geriatric syndromes One of the problems that are complicating the development and validation of the concepts of frailty and sarcopenia is that both need to be distinguished from normal age-related changes and from other age-related diseases and conditions. In fact, recent literature shows that both sarcopenia and frailty may be best understood when considered as geriatric syndromes [16–18]. The term ‘‘geriatric syndrome’’ has been commonly used in the geriatric literature for decades to define complex clinical conditions that are common in older persons and do not fit into discrete disease categories, such delirium, dementia or gait disorders. The concept of geriatric syndromes is usually well understood by any professional working in geriatric medicine, and most geriatric textbooks include a series of chapters on their diagnosis and management. However, there are some discrepancies in the understanding of such syndromes, which may be related with how sparse the literature is in conceptualizing geriatric syndromes [19,20]. Geriatric syndromes correspond to observable characteristics at the physical, morphologic and biochemical levels of an individual as determined by the genotype and the environment [21]. They capture clinical conditions in older persons that do not fit into disease categories, but are highly prevalent in old age, multifactorial, associated with multiple co-morbidities and poor outcomes, such as increased disabilities and decreased quality of life [22]. The conceptual understanding of a geriatric problem as a geriatric syndrome has been shown to be feasible and useful in predicting outcomes [23]. Geriatric syndromes have been defined as health conditions common in older persons that result from the accumulated effect of multiple predisposing factors and that may be precipitated by an acute insult. Geriatric syndromes are relevant because they are usually the presenting manifestation of multiple underlying diseases and conditions; they cause morbidity by themselves; and are only treatable when a multidimensional approach is used. Screening for geriatric syndromes seems to be more effective than using medical diagnosis in identifying frail older subjects at risk for mortality and nursing home utilization [24,25].
103
3. A syndromic approach to sarcopenia and frailty Being said that, frailty can be well understood as a geriatric syndrome. Frailty, and even isolated physical frailty, does not seem to fit into a single disease category, or to be only usual ageing. In specific life environments/conditions, it can be the consequence of a single disease and of multimorbid conditions [22]. It can be identified or defined by observing or measuring different clinical features, being the clinical manifestation of multiple underlying diseases and complex conditions. The risk of frailty increases with age and with the accumulated effects of multiple conditions and predisposing factors, and subjects identified as frail have impaired outcomes (function, morbidity, mortality, costs). Thus, it fulfills most of the characteristics that define other geriatric syndromes (i.e. delirium, falls). Frailty seems to be interlinked with other geriatric syndromes and with functional dependence, which is again consistent with our understanding of other geriatric syndromes [26]. However, frailty is an extremely complex paradigm. Research on the underlying biologic basis for frailty by studying basic homeostatic pathways and mechanisms has not yet yielded many relevant results, and these pathways seem to be extremely intricate, as shown by the growing number and complexity of the ‘‘cycles of frailty’’ published in recent years [27,28]. Moreover, the link between frailty and ageing is extremely difficult to apprehend [6]. We have also showed recently that sarcopenia is best understood as a geriatric syndrome [16]. This syndromic view has been acknowledged by the EWGSOP definition (‘‘sarcopenia is a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength or function with a risk of adverse outcomes, such as physical disability, poor quality of life and death’’) [13,14]. Nowadays, discussions are mostly focused on a better understanding of the physiopathology, the early recognition of risk factors, an integrative approach on clinical presentations (from presarcopenia to severe sarcopenia or sarcopenia with mobility disorders), complications and prevention treatment or reversibility of the loss of skeletal muscle mass, strength and function. Muscle function cannot be understood without bones. As research on osteoporosis and fractures is more advanced than research in sarcopenia and frailty [29], it is not surprising that there is a recent tendency to explore their functional links [30]. Even the term sarco-osteoporosis has been coined [31]. Sarcopenia and osteoporosis seem to be additive in predicting physical frailty [32]. Thus, studies of musculoskeletal frailty[33] are starting to be published. 4. Sarcopenia, the major determinant of physical frailty Older definitions of sarcopenia, based only on absolute or relative muscle mass, are losing relevance, as it is now clear that muscle mass, strength and function do not run parallel. The concept of frailty developed in this arena, pointing out that functional aspects were more relevantly linked to relevant health outcomes than muscle mass [34]. However, new definitions of sarcopenia have moved away from the ‘‘muscle mass only’’ concept to include muscle function and physical performance. As mentioned before, physical frailty has close links to muscle function, and therefore to the new concept and definition of sarcopenia [35,36]. The consequences of sarcopenia are mainly impaired mobility, disability for basic activities of daily living, and increased mortality. Sarcopenia is also associated with impairments in other physiological functions, including glucose regulation, hormone production, cellular communication and protein storage and turnover. In fact, many of the adverse outcomes of frailty are probably mediated by sarcopenia.
104
A.J. Cruz-Jentoft, J.-P. Michel / European Geriatric Medicine 4 (2013) 102–105
Fig. 1. A conceptual model for sarcopenia and frailty.
Disclosure of interest The authors have not supplied their declaration of conflict of interest. References [1] Rodriguez-Manas L, Feart C, Mann G, et al. Searching for an operational definition of frailty: a delphi method based consensus statement. The Frailty Operative Definition-Consensus Conference Project. J Gerontol A Biol Sci Med Sci 2012.
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Sarcopenic subjects show increased vulnerability, which is a dynamic process of negative adaptation in the face of adversity or external stressors. Sarcopenia plays a crucial etiological role in the frailty process itself, being also a key player of its latent phase and explaining numerous phenomenologies of the frailty status. Although frailty is a more complex problem that includes physical, functional, mental and social aspects, in our view sarcopenia can be considered as being a key pathway between frailty and disability (Fig. 1). There is an urgent need to obtain an operational definition of musculoskeletal health that can be used for prevention and therapy [37] and there is much confusion between these terms [38]. A better conceptualization of sarcopenia and frailty seems to be extremely relevant for the future development of geriatric medicine in its quest for preventing and fighting disability [39]. Although frailty affects both musculoskeletal and non-musculoskeletal systems, sarcopenia constitutes one of the main components of the clinical frailty syndrome [33]. Being the concept of sarcopenia closer to the musculoskeletal system (the organ system with the function of mobility), we propose that sarcopenia, using recent definitions and considered as a geriatric syndrome, is a more useful paradigm and one that may be easier to put into operational definitions than physical frailty for clinical prevention, diagnosis and intervention. This may also bring a better understanding of the physical aspects of frailty within a broader concept of frailty that includes all aspects of human life.
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