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categories: ["longevity", "bodies"]categories: ["longevity", "bodies"]tags: ["aging", "muscle", "frailty", "exercise", "clinical trials", "geriatrics"]tags: ["aging", "muscle", "frailty", "exercise", "clinical trials", "geriatrics"]summary: "The age-related loss of skeletal muscle mass, strength and function, the strongest physical predictor of late-life disability and the target of a drug pipeline that has yet to deliver."summary: "The age-related loss of skeletal muscle mass, strength and function, the strongest physical predictor of late-life disability and the target of a drug pipeline that has yet to deliver."updated: "2026-08-23"updated: "2026-11-01"humanEvidence: "Resistance training improves strength and function in randomised trials into the tenth decade of life; every drug candidate so far has added lean mass without demonstrating added function, and none is approved."humanEvidence: "Resistance training improves strength and function in randomised trials into the tenth decade of life; every drug candidate so far has added lean mass without demonstrating added function, and none is approved."------ lines 19–38 → 19–385 unchanged lines not shown
{ "label": "Principal site", "value": "Skeletal muscle" }, { "label": "Principal site", "value": "Skeletal muscle" }, { "label": "ICD-10-CM code", "value": "M62.84 (2016)" }, { "label": "ICD-10-CM code", "value": "M62.84 (2016)" }, { "label": "Diagnostic consensus", "value": "EWGSOP2 (2019)" }, { "label": "Diagnostic consensus", "value": "EWGSOP2 (2019)" }, { "label": "Prevalence over 60", "value": "~10–27%, definition-dependent" }, { "label": "Prevalence over 60", "value": "~10-27%, definition-dependent" }, { "label": "Best-evidenced treatment", "value": "Resistance training" }, { "label": "Best-evidenced treatment", "value": "Resistance training" }, { "label": "Approved drugs", "value": "None" } { "label": "Approved drugs", "value": "None" } ] ]}}`````` **Sarcopenia** is the progressive loss of skeletal muscle mass, strength and function that accompanies aging. It begins quietly in mid-adulthood, accelerates after about sixty, and by late life is the main physical substrate of frailty: the difference between rising from a chair unaided and not, between a stumble recovered and a hip fractured. It is also a test case for geroscience, because it is the age-related condition where the best treatment is unambiguous, cheap, and not a drug — and where the drug pipeline built to supplement it has so far added muscle without adding function.**Sarcopenia** is the progressive loss of skeletal muscle mass, strength and function that accompanies aging. It begins quietly in mid-adulthood, accelerates after about sixty, and by late life is the main physical substrate of frailty: it can decide whether a person rises from a chair unaided, or whether a stumble ends in recovery or a fractured hip. It is also a test case for geroscience. In sarcopenia the best treatment is unambiguous, cheap, and not a drug, and the drug pipeline built to supplement it has so far added muscle without adding function. ## From adjective to diagnosis## From adjective to diagnosis Muscle wasting in the old was described for as long as medicine has described the old, but it had no name and therefore no research programme. In 1989 the nutritionist Irwin Rosenberg, closing a meeting on nutrition and aging, argued that no decline with age is more dramatic or functionally significant than the loss of lean body mass, and proposed giving it a Greek name — sarcopenia, "poverty of flesh" — precisely so that it would be studied and measured rather than accepted.[^rosenberg1989]Physicians have described muscle wasting in the old for as long as medicine has described the old, but the condition had no name and therefore no research programme. In 1989 the nutritionist Irwin Rosenberg, closing a meeting on nutrition and aging, argued that no decline with age is more dramatic or functionally significant than the loss of lean body mass. He proposed giving it a Greek name, sarcopenia ("poverty of flesh"), so that it would be studied and measured instead of accepted.[^rosenberg1989] The gambit worked slowly. The European Working Group on Sarcopenia in Older People (EWGSOP) published the first widely adopted operational definition in 2010, combining low muscle mass with low strength or performance; its 2019 revision, EWGSOP2, inverted the order, making low strength the primary criterion, muscle quantity confirmatory, and poor physical performance a marker of severity.[^cruzjentoft2019] The reordering reflected a decade of cohort data showing that strength predicts disability and death better than mass does. In 2016 the condition received an ICD-10-CM code, M62.84 — a bureaucratic event the field's journals greeted as a milestone, because a code is what lets a condition be diagnosed, billed, counted, and targeted by a drug label.[^anker2016]The naming worked, slowly. The European Working Group on Sarcopenia in Older People (EWGSOP) published the first widely adopted operational definition in 2010, combining low muscle mass with low strength or performance; its 2019 revision, EWGSOP2, inverted the order, making low strength the primary criterion, muscle quantity confirmatory, and poor physical performance a marker of severity.[^cruzjentoft2019] The reordering reflected a decade of cohort data showing that strength predicts disability and death better than mass does. In 2016 the condition received an ICD-10-CM code, M62.84. The field's journals greeted this administrative step as a milestone, because a code is what lets a condition be diagnosed, billed, counted, and targeted by a drug label.[^anker2016] ```timeline```timeline[[lines 49–87 → 49–8710 unchanged lines not shown
## Mechanisms## Mechanisms Sarcopenia is not one process. The most direct evidence of what happens comes from whole-muscle autopsy cross-sections: the aging atrophy of the vastus lateralis reflects a loss of muscle fibres, not merely shrinkage of surviving ones, beginning around the third decade and affecting fast type II fibres disproportionately.[^lexell1988] Behind the fibre loss sits motor neuron loss — aging muscle undergoes cycles of denervation and reinnervation in which surviving motor units grow larger and less precise, which is part of why power declines faster than mass.Several processes drive sarcopenia. The most direct evidence of what happens comes from whole-muscle autopsy cross-sections: the aging atrophy of the vastus lateralis reflects a loss of muscle fibres, not merely shrinkage of surviving ones, beginning around the third decade and affecting fast type II fibres disproportionately.[^lexell1988] Behind the fibre loss sits motor neuron loss. Aging muscle undergoes cycles of denervation and reinnervation in which surviving motor units grow larger and less precise, which is part of why power declines faster than mass. Several [[hallmarks-of-aging]] converge on the tissue. Muscle stem cells (satellite cells) decline in number and regenerative capacity, the muscle-specific case of [[stem-cell-exhaustion]]. [[mitochondrial-dysfunction|Mitochondrial function]] falls, and impaired clearance of damaged mitochondria — a failure of [[autophagy]] — is the rationale for one of the few supplements tested in randomised trials. Chronic low-grade inflammation, described under [[inflammaging]], suppresses muscle protein synthesis, and senescent cells accumulating through [[cellular-senescence]] contribute to the signalling. Layered over all of this is anabolic resistance: aged muscle mounts a blunted protein-synthesis response to the same meal or the same bout of exercise that would build muscle in the young, so maintenance requires a stronger stimulus precisely when the stimulus tends to weaken.Several [[hallmarks-of-aging]] converge on the tissue. Muscle stem cells (satellite cells) decline in number and regenerative capacity, the muscle-specific case of [[stem-cell-exhaustion]]. [[mitochondrial-dysfunction|Mitochondrial function]] falls, and impaired clearance of damaged mitochondria (a failure of [[autophagy]]) is the rationale for one of the few supplements tested in randomised trials. Chronic low-grade inflammation, described under [[inflammaging]], suppresses muscle protein synthesis, and senescent cells accumulating through [[cellular-senescence]] contribute to the signalling. On top of all this sits anabolic resistance: aged muscle mounts a blunted protein-synthesis response to the same meal or bout of exercise that would build muscle in the young. Maintaining muscle therefore takes a stronger stimulus at the stage of life when the stimulus tends to weaken. Disuse amplifies everything. Bed rest strips muscle from an older adult in days, and the resemblance between sarcopenia and the deconditioning of spaceflight is close enough that countermeasure research crosses between geriatrics and [[microgravity-adaptation|space physiology]].Disuse amplifies all of these processes. Bed rest strips muscle from an older adult in days, and sarcopenia resembles the deconditioning of spaceflight closely enough that countermeasure research crosses between geriatrics and [[microgravity-adaptation|space physiology]]. ## Scale and consequences## Scale and consequences How common sarcopenia is depends almost entirely on whose definition is applied. A 2022 systematic review and meta-analysis put global prevalence between roughly 10% and 27% in people aged sixty and over, with the spread driven more by the choice of diagnostic criteria than by geography.[^petermannrocha2022] That instability is not a footnote; it is one of the field's central problems, discussed below.How common sarcopenia is depends almost entirely on whose definition is applied. A 2022 systematic review and meta-analysis put global prevalence between roughly 10% and 27% in people aged sixty and over, with the spread driven more by the choice of diagnostic criteria than by geography.[^petermannrocha2022] That instability is one of the field's central problems, discussed below. The consequences are better established than the prevalence. Low grip strength and slow gait speed — the measures at the heart of every definition — predict falls, hospitalisation, loss of independence and death across large cohorts, which is why they serve as endpoints in trials and why muscle is considered the most tractable domain in [[aging-biomarkers|functional aging measurement]] and in the [[xprize-healthspan]] competition. Sarcopenia also interacts with the era's dominant pharmacology: [[glp-1-receptor-agonists]] produce substantial weight loss of which a meaningful fraction is lean tissue, and preserving muscle during pharmacological weight loss has become the commercial question pulling muscle-drug candidates away from sarcopenia itself.The consequences are better established than the prevalence. Low grip strength and slow gait speed, the measures at the heart of every definition, predict falls, hospitalisation, loss of independence and death across large cohorts. That is why they serve as trial endpoints, and why muscle is considered the most tractable domain in [[aging-biomarkers|functional aging measurement]] and in the [[xprize-healthspan]] competition. Sarcopenia also interacts with the era's dominant pharmacology. [[glp-1-receptor-agonists]] produce substantial weight loss, a meaningful fraction of it lean tissue, and preserving muscle during pharmacological weight loss has become the commercial question pulling muscle-drug candidates away from sarcopenia itself. > [!key] Mass is not function> [!key] Mass is not function> Every drug that has entered trials for sarcopenia has been judged, implicitly, on the assumption that added muscle means added ability. The trials keep severing that link: lean mass rises on drug after drug while strength and performance do not. Until a molecule moves a functional endpoint, muscle mass remains an unvalidated surrogate — and regulators treat it as one.> Every drug that has entered trials for sarcopenia has been judged on the implicit assumption that added muscle means added ability. The trials keep breaking that link: lean mass rises on drug after drug while strength and performance do not. Until a molecule moves a functional endpoint, muscle mass remains an unvalidated surrogate, and regulators treat it as one. ## What works## What works The intervention with unambiguous evidence is progressive resistance exercise, and the evidence reaches further into old age than intuition suggests. In 1990, Fiatarone and colleagues put frail nursing-home residents around age ninety through eight weeks of high-intensity strength training: strength gains averaged 174%, mid-thigh muscle area grew about 9%, and gait speed improved; a larger randomised trial in 1994 confirmed that training, unlike nutritional supplementation alone, improved strength and mobility in the very old.[^fiatarone1990] Nothing in the drug pipeline has approached effects of that size. The broader case for training as the benchmark geroprotective intervention is made at [[exercise-and-aging]].The intervention with unambiguous evidence is progressive resistance exercise, and the evidence reaches further into old age than intuition suggests. In 1990, Fiatarone and colleagues put frail nursing-home residents around age ninety through eight weeks of high-intensity strength training. Strength gains averaged 174%, mid-thigh muscle area grew about 9%, and gait speed improved. A larger randomised trial in 1994 confirmed that training, unlike nutritional supplementation alone, improved strength and mobility in the very old.[^fiatarone1990] Nothing in the drug pipeline has approached effects of that size. The broader case for training as the benchmark geroprotective intervention is made at [[exercise-and-aging]]. Nutrition matters at the margins. Anabolic resistance implies older adults need a stronger protein stimulus, and several consensus groups recommend higher intakes in older age, though trial evidence for supplementation is clearest in people who are undernourished and modest in those who are not. The [[dietary-supplements|supplement market]] runs well ahead of that evidence. Conversely, severe [[caloric-restriction]] — the best-studied lifespan intervention in animals — costs lean mass, which is a principal reason it translates poorly to the population that already has sarcopenia.Nutrition matters at the margins. Anabolic resistance implies that older adults need a stronger protein stimulus, and several consensus groups recommend higher intakes in older age. Trial evidence for supplementation, though, is clearest in people who are undernourished and modest in those who are not. The [[dietary-supplements|supplement market]] runs well ahead of that evidence. Severe [[caloric-restriction]], the best-studied lifespan intervention in animals, works against muscle: it costs lean mass, a principal reason it translates poorly to the population that already has sarcopenia. ## The drug pipeline## The drug pipeline The pipeline's history is a single lesson taught repeatedly. Myostatin, the negative regulator of muscle growth discovered in 1997, made muscle one of the most druggable tissues in the body, and [[myostatin-inhibition]] became the field's flagship approach. In a phase 2 trial in weak older adults who had fallen, the antibody LY2495655 increased appendicular lean mass but not grip strength; bimagrumab, an antibody blocking the activin type II receptors, likewise increased lean mass and cut fat mass in older adults with sarcopenia while physical function improved no more than in the control arm, which had received only nutrition advice and light exercise.[^becker2015] Bimagrumab's subsequent path is telling: licensed out of Novartis, acquired with Versanis by Eli Lilly in 2023, it is now developed for preserving lean mass during pharmacological weight loss — a market with a measurable surrogate endpoint — rather than for sarcopenia.The pipeline's history repeats one result. Myostatin, the negative regulator of muscle growth discovered in 1997, made muscle one of the most druggable tissues in the body, and [[myostatin-inhibition]] became the field's flagship approach. In a phase 2 trial in weak older adults who had fallen, the antibody LY2495655 increased appendicular lean mass but not grip strength. Bimagrumab, an antibody blocking the activin type II receptors, likewise increased lean mass and cut fat mass in older adults with sarcopenia, while physical function improved no more than in the control arm, which had received only nutrition advice and light exercise.[^becker2015] Bimagrumab was later licensed out of Novartis and acquired with Versanis by Eli Lilly in 2023. It is now developed for preserving lean mass during pharmacological weight loss, a market with a measurable surrogate endpoint, rather than for sarcopenia. Newer mechanisms have fared no better so far. Azelaprag, an oral apelin-receptor agonist developed by BioAge Labs on the rationale that apelin is an exercise-induced signal that declines with age, had shown prevention of muscle atrophy during bed rest in a small phase 1b study; its phase 2 obesity trial alongside tirzepatide was discontinued in December 2024 after liver-enzyme elevations in the azelaprag arms.[^bioage2024] Urolithin A, a gut-microbiome metabolite that stimulates mitophagy, is sold as a supplement and has been tested in randomised trials: in sixty-six sedentary adults aged 65 to 90, four months of supplementation improved a muscle-endurance measure at two months, but six-minute walk distance and other outcomes did not separate from placebo.[^liu2022] As of 2026 no regulator has approved any drug for sarcopenia.Newer mechanisms have fared no better so far. Azelaprag, an oral apelin-receptor agonist developed by BioAge Labs on the rationale that apelin is an exercise-induced signal that declines with age, had shown prevention of muscle atrophy during bed rest in a small phase 1b study; its phase 2 obesity trial alongside tirzepatide was discontinued in December 2024 after liver-enzyme elevations in the azelaprag arms.[^bioage2024] Urolithin A, a gut-microbiome metabolite that stimulates mitophagy, is sold as a supplement and has been tested in randomised trials. In sixty-six sedentary adults aged 65 to 90, four months of supplementation improved a muscle-endurance measure at two months, but six-minute walk distance and other outcomes did not separate from placebo.[^liu2022] As of 2026 no regulator has approved any drug for sarcopenia. ## Open problems## Open problems > [!caution] The definition moves under the trials> [!caution] The definition moves under the trials> EWGSOP, EWGSOP2, the Asian and international working groups, and the US FNIH project draw different cut-offs on different measures, and prevalence in the same population can shift several-fold depending on which is applied. Trials recruited under one definition cannot be cleanly compared with trials recruited under another, and a regulator asked to approve a sarcopenia drug has no consensus endpoint to approve it against. The 2024 GLIS consensus settled the concept — muscle mass plus strength, with function relegated to an outcome — but deliberately deferred the operational cut-offs, so the harmonisation the pipeline needs is still pending.[^kirk2024]> EWGSOP, EWGSOP2, the Asian and international working groups, and the US FNIH project draw different cut-offs on different measures, and prevalence in the same population can shift several-fold depending on which is applied. Trials recruited under one definition cannot be cleanly compared with trials recruited under another, and a regulator asked to approve a sarcopenia drug has no consensus endpoint to approve it against. The 2024 GLIS consensus settled the concept (muscle mass plus strength, with function relegated to an outcome) but deliberately deferred the operational cut-offs, so the harmonisation the pipeline needs is still pending.[^kirk2024] Beneath the definitional problem sits a biological one: whether sarcopenia is a disease to be treated or simply aging seen in one tissue. The [[geroscience-hypothesis]] reads it as the latter — one output of shared hallmark processes, unlikely to yield to a muscle-only intervention any more than [[immunosenescence]] has yielded to an immune-only one. The counterargument is practical: whatever its ultimate cause, sarcopenia has cheap validated endpoints, a code, and an intervention that works, which makes muscle the arena where a [[compression-of-morbidity|compressed morbidity]] is easiest to demonstrate. The uncomfortable fact for the field is that the comparator any future drug must beat is resistance training — an intervention with effect sizes no molecule has matched, available now, and taken up by only a minority of the people whose remaining [[healthspan]] most depends on it.Beneath the definitional problem sits a biological one: whether sarcopenia is a disease to be treated or simply aging seen in one tissue. The [[geroscience-hypothesis]] reads it as the latter: one output of shared hallmark processes, no more likely to yield to a muscle-only intervention than [[immunosenescence]] has yielded to an immune-only one. The counterargument is practical. Whatever its ultimate cause, sarcopenia has cheap validated endpoints, a code, and an intervention that works, which makes muscle the easiest place to demonstrate a [[compression-of-morbidity|compressed morbidity]]. The uncomfortable fact for the field is that any future drug must beat resistance training, an intervention with effect sizes no molecule has matched. It is available now, yet only a minority of the people whose remaining [[healthspan]] most depends on it take it up. ## See also## See also lines 92–97 → 92–984 unchanged lines not shown
- [[aging-biomarkers]]- [[aging-biomarkers]]- [[healthspan]]- [[healthspan]]- [[inflammaging]]- [[inflammaging]]- [[retatrutide]] ## References## References lines 99–108 → 100–1091 unchanged line not shown
[^cruzjentoft2019]: `paper` Cruz-Jentoft, A. J. et al. "Sarcopenia: European consensus on definition and diagnosis." *Age and Ageing*, 2010; and Cruz-Jentoft, A. J. et al. "Sarcopenia: revised European consensus on definition and diagnosis (EWGSOP2)." *Age and Ageing*, 2019. {The 2019 revision made low strength the primary criterion, reversing the 2010 mass-first ordering.}[^cruzjentoft2019]: `paper` Cruz-Jentoft, A. J. et al. "Sarcopenia: European consensus on definition and diagnosis." *Age and Ageing*, 2010; and Cruz-Jentoft, A. J. et al. "Sarcopenia: revised European consensus on definition and diagnosis (EWGSOP2)." *Age and Ageing*, 2019. {The 2019 revision made low strength the primary criterion, reversing the 2010 mass-first ordering.}[^anker2016]: `paper` Anker, S. D., Morley, J. E. and von Haehling, S. "Welcome to the ICD-10 code for sarcopenia." *Journal of Cachexia, Sarcopenia and Muscle*, 2016. {An editorial marking the assignment of ICD-10-CM code M62.84, effective October 2016.}[^anker2016]: `paper` Anker, S. D., Morley, J. E. and von Haehling, S. "Welcome to the ICD-10 code for sarcopenia." *Journal of Cachexia, Sarcopenia and Muscle*, 2016. {An editorial marking the assignment of ICD-10-CM code M62.84, effective October 2016.}[^lexell1988]: `paper` Lexell, J., Taylor, C. C. and Sjöström, M. "What is the cause of the ageing atrophy? Total number, size and proportion of different fiber types studied in whole vastus lateralis muscle from 15- to 83-year-old men." *Journal of Neurological Sciences*, 1988.[^lexell1988]: `paper` Lexell, J., Taylor, C. C. and Sjöström, M. "What is the cause of the ageing atrophy? Total number, size and proportion of different fiber types studied in whole vastus lateralis muscle from 15- to 83-year-old men." *Journal of Neurological Sciences*, 1988.[^petermannrocha2022]: `paper` Petermann-Rocha, F. et al. "Global prevalence of sarcopenia and severe sarcopenia: a systematic review and meta-analysis." *Journal of Cachexia, Sarcopenia and Muscle*, 2022. {Prevalence ranged roughly 10–27% in adults 60 and over, with the choice of diagnostic classification the main driver of the spread.}[^petermannrocha2022]: `paper` Petermann-Rocha, F. et al. "Global prevalence of sarcopenia and severe sarcopenia: a systematic review and meta-analysis." *Journal of Cachexia, Sarcopenia and Muscle*, 2022. {Prevalence ranged roughly 10-27% in adults 60 and over, with the choice of diagnostic classification the main driver of the spread.}[^fiatarone1990]: `paper` Fiatarone, M. A. et al. "High-intensity strength training in nonagenarians: effects on skeletal muscle." *JAMA*, 1990; and Fiatarone, M. A. et al. "Exercise training and nutritional supplementation for physical frailty in very elderly people." *New England Journal of Medicine*, 1994. {The 1990 study was ten institutionalised volunteers with no placebo arm; the 1994 trial randomised 100 residents and found supplementation without exercise did nothing.}[^fiatarone1990]: `paper` Fiatarone, M. A. et al. "High-intensity strength training in nonagenarians: effects on skeletal muscle." *JAMA*, 1990; and Fiatarone, M. A. et al. "Exercise training and nutritional supplementation for physical frailty in very elderly people." *New England Journal of Medicine*, 1994. {The 1990 study was ten institutionalised volunteers with no placebo arm; the 1994 trial randomised 100 residents and found supplementation without exercise did nothing.}[^becker2015]: `paper` Becker, C. et al. "Myostatin antibody (LY2495655) in older weak fallers: a proof-of-concept, randomised, phase 2 trial." *The Lancet Diabetes & Endocrinology*, 2015; and Rooks, D. et al. "Bimagrumab vs Optimized Standard of Care for Treatment of Sarcopenia in Community-Dwelling Older Adults: A Randomized Clinical Trial." *JAMA Network Open*, 2020. {In both trials lean mass rose on drug; grip strength did not improve in the first, and function improved equally in both arms of the second.}[^becker2015]: `paper` Becker, C. et al. "Myostatin antibody (LY2495655) in older weak fallers: a proof-of-concept, randomised, phase 2 trial." *The Lancet Diabetes & Endocrinology*, 2015; and Rooks, D. et al. "Bimagrumab vs Optimized Standard of Care for Treatment of Sarcopenia in Community-Dwelling Older Adults: A Randomized Clinical Trial." *JAMA Network Open*, 2020. {In both trials lean mass rose on drug; grip strength did not improve in the first, and function improved equally in both arms of the second.}[^bioage2024]: `statement` BioAge Labs. "BioAge Labs Announces Discontinuation of STRIDES Phase 2 Clinical Trial Evaluating Azelaprag in Combination with Tirzepatide for the Treatment of Obesity." Press release, December 2024. {The company reported transaminase elevations in 11 of 204 participants, all in azelaprag-containing arms, without clinically significant symptoms.}[^bioage2024]: `statement` BioAge Labs. "BioAge Labs Announces Discontinuation of STRIDES Phase 2 Clinical Trial Evaluating Azelaprag in Combination with Tirzepatide for the Treatment of Obesity." Press release, December 2024. {The company reported transaminase elevations in 11 of 204 participants, all in azelaprag-containing arms, without clinically significant symptoms.}[^liu2022]: `paper` Liu, S. et al. "Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial." *JAMA Network Open*, 2022. {Sixty-six sedentary adults aged 65–90; an endurance measure improved versus placebo at two months but the difference was no longer significant at four.}[^liu2022]: `paper` Liu, S. et al. "Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial." *JAMA Network Open*, 2022. {Sixty-six sedentary adults aged 65-90; an endurance measure improved versus placebo at two months but the difference was no longer significant at four.}[^kirk2024]: `paper` Kirk, B., Cawthon, P. M. et al. "The Conceptual Definition of Sarcopenia: Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS)." *Age and Ageing*, 2024. {A conceptual definition only; the consensus explicitly left operational cut-points to future work.}[^kirk2024]: `paper` Kirk, B., Cawthon, P. M. et al. "The Conceptual Definition of Sarcopenia: Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS)." *Age and Ageing*, 2024. {A conceptual definition only; the consensus explicitly left operational cut-points to future work.} removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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