Evaluation of Sarcopenia

Sarcopenia is extensively documented in the literature and belongs to the hot topics within the geriatric and gerontological research domains (1). Due to sarcopenia, activities of daily living in elderly persons necessitate efforts close to the maximal strength and loss of independency can occur (2). Sarcopenia-induced muscle weakness is therefore a typical characteristic of frailty, one of the major geriatric syndromes (3). The total cost of health care directly induced by sarcopenia in the United States of America for the year 2000 reached 18.5 billion dollar (4). It is to be expected that, given the worldwide ageing of the population, the cost will further increase, not only in industrialized, but also in developing countries. Therefore, accurate assessment of the muscle morphology and functional capacity should be part of the comprehensive assessment of each geriatric patient for early detection and start of preventive and/or treatment interventions.

Assessment tools for sarcopenia described in the literature are mainly derived from the operational definitions adopted. Conceptually, sarcopenia has been defined as age-related loss of muscle mass and muscle strength; a phenomenon occurring in all ageing humans and animals. Several situations and contextual factors can lead to a dramatic acceleration of the process, thus leading to loss of physical dependency in the elderly patient. Moreover, the required muscle components mandatory for physical independency show high inter-individual variability and depend on both intrinsic factors (body weight, co-morbidity, etc.) and external factors (physical environment of the patient, etc.). Evaluation tools able to identify these geriatric patients at risk for rapid progression of sarcopenia are therefore of high clinical importance. A supplementary element in this context is the fact that the muscle weakness due to sarcopenia is more important than can be explained by atrophy alone. Therefore, assessment tools based only on muscle mass might under-estimate the (risk for) functional disabilities due to sarcopenia.

This lecture will provide a critical overview of the most common assessment tools for sarcopenia described in the literature. These can be divided in several categories depending on their target (muscle atrophy versus muscle performance) and clinical utility (diagnosis and categorization versus evaluation of changes over time). Also, some new and more experimental evaluation instruments and future developments will be briefly discussed.


References

1. Morley JE (2004) Editorial: The top 10 hot topics in aging. J Gerontol A Biol Sci Med Sci 59A:24-33.
2. Hortobagyi T, Mizelle C, Beam S, DeVita P (2003) Old adults perform activities of daily living near their maximal capabilities. J Gerontol A Biol Sci Med Sci 58:M453-460.
3. Fried LP, Tangen CM, Walston J, Newman AB, Hirsch C, Gottdiener J, Seeman T, Tracy R, Kop WJ, Burke G, McBurnie MA (2001) Frailty in Older Adults: Evidence for a Phenotype. J Gerontol A Biol Sci Med Sci 56:M146-157.
4. Janssen I, Shepard DS, Katzmarzyk PT, Roubenoff R (2004) The healthcare costs of sarcopenia in the United States. J Am Geriatr Soc 52:80-85.