Muscle mass alone, measured multiple different ways, is not consistently a strong predictor of entrent or future function.
Muscle strength is a consistent, strong predictor of current and future function and weakness should be considered the key clinical indicator.
Muscle impairment, reflected as weakness. is likely to be a geriatric syndrome in which there are multiple potential concurrent pathophysiological contributors.
Since functional performance is influenced by both impairments and compensations, it may be mat superior capacity in some elements can compensate for deficits in others, and improving strength might improve function even in the face of other impairments. In particular, integrity of muscle strength has a fundamental role in compensating for impaired physical function due to neurological problems. Thus, effective prevention and treatment of sarcopenia in older people can be important even when the primary cause of impairment is not sarcopenia.
Epidemiological approaches that nave been used to develop a definition of muscle impairment and assess the possible role of muscle quantity and quality should be complemented by analyses driven by a clinical perspective. The diagnosis of “poor muscle strength” in older persons is tampered by the lack of availability of reference data, especially from healthy older people at the end of the age spectrum. In fact, most of the available data for people 85+ are from small series and in unselected individuals, often affected by substantial morbidity.
We should take a clinical perspective in our research. We can approach the problem as clinician would: work backwards from a “chief complaint” and clinical findings, eventually ending up at diagnostic strategies that might be useful for prognosis and treatment. An example could be those who present with mobility problems by self report or performance, then are assessed for muscle strength. Among weak persons with a mobility problem who should be assessed for low muscle mass? We may need to separate research issues related to strength from those related to strength combined with muscle mass. We cannot address this problem if we do not develop age-specific criteria for “poor strength”
We should use data sets that include a wide range of muscle impairment and mobility disability and may want to include clinical as well as population-based samples.
We need to consider what conditions or clinical findings should be considered “exclusions” from further analyses. Eg ?stroke parkinsons
