Tools in the assessment of sarcopenia

Abstract

This review provides a framework for the development of an operational definition of sarcopenia and of the potential end points that might be adopted in clinical trials among older adults. While the clinical relevance of sarcopenia is widely recognized, there is currently no universally accepted definition of the disorder. The development of interventions to alter the natural history of sarcopenia also requires consensus on the most appropriate end points for determining outcomes of clinical importance which might be utilized in intervention studies. We review current approaches to the definition of sarcopenia and the methods used for the assessment of various aspects of physical function in older people. The potential end points of muscle mass, muscle strength, muscle power, and muscle fatigue, as well as the relationships between them, are explored with reference to the availability and practicality of the available methods for measuring these end points in clinical trials. Based on current evidence, none of the four potential outcomes in question is sufficiently comprehensive to recommend as a uniform single outcome in randomized clinical trials. We propose that sarcopenia may be optimally defined (for the purposes of clinical trial inclusion criteria as well as epidemiological studies) using a combination of measures of muscle mass and physical performance. The choice of outcome measures for clinical trials in sarcopenia is more difficult; co-primary outcomes, tailored to the specific intervention in question, may be the best way forward in this difficult but clinically important area.

Fig. 1

Mass/strength divergence in older men and women taking part in the Health, Aging and Body Composition Study.Maintenance or gaining lean muscle mass did not prevent aging-associated declines in muscle strength, with men losing almost twice as much strength as women. Reprinted from [28] with permission.

Fig.2

Muscle fibre size is positively correlated with muscle strength. Among 41 older men, 1-RM leg extension (kg) was significantly associated with muscle fibre cross-sectional area (r=0.45; p<0.001).Muscle fibre cross-sectional area was significantly lower in type II than in type I fibres (p<0.01). Greater muscle fibre cross-sectional area was associated with greater thigh muscle area and muscle strength (0.30 ≤ r ≤ 0.45; p<0.05). Reprinted from [27] with permission.

Fig.3

1-RM leg extension vs handgrip strength in healthy elderly men and women. Scatter plot for correlation of 1-RM leg extension with handgrip strength in elderly men (open circles) and elderly women (filled circles). Line represents the fitted regression. Pearson correlation coefficient was 0.78 (p<0.001)