8Sarcopenia
Introduction
Sarcopenia is characterised by generalised and progressive loss of muscle mass, reduction in muscle strength and resultant functional impairment. The condition is associated with poor health outcomes and premature death [1], [2] and has recently been included under a single code in the International Classification of Disease (ICD-10) [3]. Sarcopenia is associated with a significant burden on the global health economy, calculated at $18.5 billion in the US in 2004, but more recently calculated to cost £2 billion in the UK [4]. The prevalence varies with location and definition; however, it is estimated to be up to 29% of older persons in the setting of community healthcare and 14%–33% for those in long-term care [1]. This emphasises the importance of this condition, and the need to increase awareness of the condition amongst clinicians, researchers, health economists and policy-makers.
This chapter highlights the scientific narrative that has led to the current definition of sarcopenia and discusses the epidemiology of the condition. We provide information regarding the assessment of sarcopenia in both clinical and research contexts and provide a summary of current therapeutic options.
Section snippets
Definition
The description of muscle mass loss in extreme old age was first made by Critchley in 1931, with a particular observation that this was most marked at the hands and feet. However, the term ‘sarcopenia’ was first coined in 1984 by Rosenberg, who used it in the context of the age-related loss of muscle mass (ICD1). This definition was used and built on by Baumgartner and colleagues, who defined muscle mass as appendicular lean mass (ALM) divided by height and showed that, using this parameter,
Clinical development
Sarcopenia can be precipitated by a number of factors, including age, nutritional deficiencies, hormonal changes, metabolic disturbance, comorbidities, inflammation, drug adverse effects, genetic predisposition and the effect of early environment. This results in reduction in muscle mass and strength, leading to sarcopenic status. This in turn leads to weakness and a reduced mobility, with downstream deconditioning and reduced physiological reserve. This in turn leads to propensity for reduced
Epidemiology
Under this sub-heading, we explore the effect of epidemiological parameters on the individual facets of sarcopenia: muscle mass, muscle strength, and physical function.
Screening
Formal assessments may not be appropriate for the screening of patients in primary care because of availability of equipment, expertise and cost. In this context, screening tools are necessary to filter out those patients requiring specialist consultation and assessment.
These screening tools include the ‘Red Flag’ approach, which uses clinician-observed or patient-reported parameters to assess the degree of risk of sarcopenia. This include general weakness, visible muscle loss, reduced walking
Assessment
To be able to diagnose or comments on the extent of sarcopenia, robust methods for assessment are required. This sub-section of the chapter will pertain to the methodologies used for the assessment of sarcopenia in both clinical and research contexts, and a summary is shown in Table 2.
Therapy
The basic therapeutic options for the management of sarcopenia include resistance exercise, increasing protein intake and 25-OH-vitamin D supplementation if required. However, new discoveries regarding the pathogenesis of sarcopenia have led to the development of novel therapeutic agents. This subsection of the chapter will cover the essentials element of treatments for sarcopenia, and a summary of these is seen in Fig. 4.
Conflicts of interest
None to declare.
Disclosures
None.
Acknowledgements
The authors are supported by funding from the Medical Research Council, National Institute of Health Research and the University of Southampton.
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