(inferred from Cruz-Jentoft et al., 2018) The operational definition of sarcopenia — the EWGSOP2 (2019) European consensus, now paired with de Santana’s SR-MA for the prognostic (mass -> mortality) evidence the definition alone does not carry. The definitional object here is a case definition + diagnostic algorithm, not a treatment-effect estimate. A definition is not an outcome finding: the predictive claims below are prognostic association the group asserts, and the cut-offs are normative (set against a healthy-young reference, not validated against outcomes).
Why it matters — the reversal from mass to strength
(Cruz-Jentoft et al., 2018) Sarcopenia is «a progressive and generalised skeletal muscle disorder» (a muscle disease / muscle failure) tied to falls, fractures, disability and mortality. The decision-relevant move is what you measure to detect it, and EWGSOP2 inverts three decades of practice:
- pre-2010: low muscle mass only;
- EWGSOP 2010: added muscle function to mass;
- EWGSOP2 2019: strength first — «muscle strength comes to the forefront, as it is recognised that strength is better than mass in predicting adverse outcomes». Muscle mass is demoted to a confirmatory role; physical performance, «formerly considered part of the core definition», is demoted again to grading severity only.
Why mass lost primacy: strength predicts the outcomes better, AND mass/quality «remain problematic as primary parameters» because they are technically hard to measure. This is the Surrogate Outcomes discipline enacted on a case definition — the easy-to-image quantity (mass) was the well-lit surrogate; strength and function are closer to what the patient cares about (staying on their feet, independent).
But the demotion is relative, not a dismissal — mass still independently predicts mortality (de Santana 2021). EWGSOP2’s «strength is better than mass» is a claim about which is the better/primary predictor; it is not a finding that mass carries no signal. de Santana’s gold-tier SR-MA (9 cohorts, n=10,028 community-dwelling non-frail ≥65) finds low appendicular muscle mass «inversely associated with mortality» (ASMI SMD −0.18, 95% CI −0.23 to −0.12) and — the refinement — the link «cannot be completely explained by differences in muscle strength» (grip-strength was a non-significant, underpowered meta-regression moderator, so mass’s independent signal is consistent with the data, not proven by it). So «not only skeletal muscle quality matters … but also its quantity» (de Santana et al., 2021). This refines, does not contradict, the demotion (not-joined check (ii): different scope — primary predictor vs independent signal; both hold): keep strength as the primary screen (cheaper, more reliable, better single predictor), but read mass as prognostically load-bearing, most of all in the overweight/obese older adult where the mass-mortality link is strongest. Magnitude, modifiers, and the predictor-vs-target line live on -> Low Muscle Mass and Mortality. It remains a predictor, not a proven treatment target — no RCT shows raising mass cuts mortality, so the open loop below stands.
The three-state operational definition
| State | Trigger | What it means |
|---|---|---|
| Probable | low muscle strength | enough to start assessment + treatment |
| Confirmed | + low muscle quantity or quality | the diagnosis is made |
| Severe | + low physical performance | «When low muscle strength, low muscle quantity/quality and low physical performance are all detected, sarcopenia is considered severe» |
EWGSOP2 «uses low muscle strength as the primary parameter of sarcopenia; muscle strength is presently the most reliable measure of muscle function». Sarcopenia is probable on low strength alone — so treatment need not wait for imaging.
Tests / indicators — the F-A-C-S algorithm
(Cruz-Jentoft et al., 2018) Find -> Assess -> Confirm -> Severity:
- Find — SARC-F questionnaire (self-reported; high specificity, low-to-moderate sensitivity, so it «will mostly detect severe cases»).
- Assess strength — grip strength (calibrated dynamometer; a reliable surrogate for whole-body strength) or chair-stand (five rises, a leg-strength proxy). The prognostic weight behind screening on strength is now held at scale: low grip predicts all-cause + cause-specific mortality (Celis-Morales, UK Biobank n=502,293) and adds discrimination to an office-based risk score -> Grip Strength and Mortality; Celis-Morales used the near-identical FNIH weakness cut-off (<26 kg men / <16 kg women).
- Confirm quantity — DXA or BIA in clinical care; DXA/MRI/CT in research. (Calf circumference <31 cm is a low-resource proxy where no instrument is available.)
- Severity — gait speed (the advised measure), SPPB, TUG, or 400-m walk.
Cut-off points (EWGSOP2 Table 3)
| Domain | Test | Men | Women |
|---|---|---|---|
| Strength | grip strength | <27 kg | <16 kg |
| Strength | chair stand (5 rises) | >15 s | >15 s |
| Quantity | ASM | <20 kg | <15 kg |
| Quantity | ASM/height² | <7.0 kg/m² | <5.5 kg/m² |
| Performance | gait speed | ≤0.8 m/s | ≤0.8 m/s |
| Performance | SPPB | ≤8 points | ≤8 points |
| Performance | TUG | ≥20 s | ≥20 s |
| Performance | 400-m walk | non-completion or ≥6 min | non-completion or ≥6 min |
These thresholds are normative, not outcome-validated (Cruz-Jentoft et al., 2018): set against a healthy-young-adult reference, usually at -2 SD (-2.5 SD for a conservative diagnosis), rounded for ease of use — «minor reduction in accuracy» accepted for usability. A threshold quoted here marks the edge of a reference distribution, not a knee in a dose-response curve.
Categories
- Primary (age-related, no other cause) vs secondary (a systemic/inflammatory disease, physical inactivity, or inadequate energy/protein intake) — the secondary causes are the modifiable handle and name the levers: activity and protein -> Protein and Resistance Training for Muscle and Strength. The protein handle is stratum-specific here: aging raises the per-meal protein/leucine threshold (Anabolic Resistance), so the older-adult target (1.0-1.2 g/kg/d, ~25-30 g protein per meal) sits above the general-adult RDA -> Protein Intake for Older Adults.
- Acute (<6 months, usually acute illness/injury) vs chronic (≥6 months, progressive, raises mortality risk) — newly introduced to motivate periodic reassessment so decline is caught early.
- Sarcopenic obesity (reduced lean mass + excess adiposity; obesity worsens sarcopenia via fat
infiltration, lower function, higher mortality) is «a distinct condition … outside of the scope of
this article» — EWGSOP2 sets no formal cut-off for it. So the pages that invoke sarcopenic obesity
(Menopause and the Shifting Levers, Big Rocks (Elderly)) rest on a construct with no agreed
operational definition (
type-Ggap).
Decision relevance
(inferred from Cruz-Jentoft et al., 2018)
- Measure strength, not the scale or the DXA number, to screen. Low grip strength or a slow chair-stand is enough to flag probable sarcopenia and act — imaging confirms, it does not gate the first intervention. This is why body weight / BMI / lean-mass alone mislead in the elderly stratum.
- Strength falls faster than mass. After 50, leg mass declines 1-2%/year but strength 1.5-5%/year (Cruz-Jentoft et al., 2018) — muscle quality degrades, so a mass number under-reads the functional loss. A second reason mass is the weaker marker.
- The levers are the ones already ranked — resistance training + adequate protein (Protein and Resistance Training for Muscle and Strength), and muscle-strengthening activity (Muscle-Strengthening Activity and Mortality). EWGSOP2 asserts nutrition + exercise «seem to slow or reverse» the process; that is consensus, not a validated effect (the intervention evidence lives on those pages, not here). In the diagnosed-sarcopenic stratum specifically, a moderate-tier MA (Song 2023, 12 trials, «713 older adults diagnosed with sarcopenia») found adding a compound protein+vitamin-D supplement to resistance training «further enhance[d] grip strength rather than muscle mass» — a borderline grip effect (WMD 1.87, 95% CI 0.01-3.74, P=0.049; heterogeneous, compound-confounded), null on mass (Song et al., 2023). It nudges the EWGSOP2 strength criterion, not the mass one — consistent with steering toward function -> Protein and Resistance Training for Muscle and Strength holds the full stratum picture and its weight caveats.
- The outcome to steer toward is function, not mass — falls avoided, independence retained. Muscle mass is a surrogate; strength and performance sit closer to the patient-important outcome -> Surrogate Outcomes, Rating Outcome Importance.
Limits — the open loop
(inferred from Cruz-Jentoft et al., 2018; de Santana et al., 2021)
- The definition is single-source consensus. The case definition, algorithm and cut-offs are EWGSOP2 expert working-group synthesis, not a systematic review; symmetric standards apply — the cut-offs and the strength-over-mass claim are asserted with narrative backing, not a pooled effect estimate. The one cross-source addition is de Santana’s SR-MA on the mass -> mortality prognosis (above), which is observational.
- Cut-offs are normative, not outcome-anchored (−2 SD vs healthy young), so they answer is this person low vs a young reference?, not below what value does risk rise?.
- Sarcopenic obesity undefined (above) — a named
type-Ggap the downstream pages inherit. - A definition grades nothing against a realized outcome. The loop is open: this page holds how to identify sarcopenia, not proof that treating it changes what a person experiences.
Sarcopenia is not frailty (boundary note)
(inferred from Vermeiren et al., 2016) Sarcopenia is the muscle-specific disorder; Frailty is the broader multisystem reserve-capacity syndrome that names sarcopenia (weakness, slow gait, weight loss) as a major physical driver but also spans cognitive/psychosocial/medical deficits sarcopenia excludes. Physical-focus frailty instruments (Fried phenotype) overlap this page’s strength/performance measures heavily; multidomain and deficit-accumulation frailty indices do not. Keep the objects distinct: a person can be sarcopenic without being frail, and frail without being (primarily) sarcopenic.