Changes in body composition occur with normal physiological ageing ; usually, body weight increases during adulthood and peaks at the age of 65 years in women and 54 years in men . Muscle mass is lost at a rate of approximately 8% per decade between the ages 50 and 70 years; then weight loss is coupled with an accelerated loss of muscle mass, reaching a rate of 15% each decade . The overall prevalence of sarcopenia is reported to be 10% ; with the continued increase in the older population, sarcopenia is becoming a serious global public health problem.
Sarcopenia is associated with the ageing process ; loss of muscle mass and strength, which in turn affects balance, gait and overall ability to perform tasks of daily living, are hallmarks of this disease that is also a powerful predictor of disability . The risk of disability is 1.5–4.6 times higher in older people with sarcopenia than in those with normal muscle. These common age-related changes in skeletal muscle are major causes of impaired physical function in older adults, contributing to impaired mobility, falls and hospitalisation. The causes of sarcopenia are multifactorial and can include muscle disuse, changing endocrine function, chronic diseases, inflammation, insulin resistance and nutritional deficiencies ; reductions in testosterone and oestrogen that accompany ageing appear to accelerate its development .
2.3.1 Screening and Assessment for Sarcopenia
Sarcopenia, like many other health conditions, is asymptomatic in its initial stages, when interventions can best prevent the adverse health outcomes . Screening is currently not a routine aspect of clinical practice, partly because of the lack of appropriate screening strategies . An ideal screening test should be cheap, acceptable and easily implementable without requiring additional training . Several expert groups have convened with the goal of establishing a consensus about diagnostic criteria for sarcopenia [43,44,45,46]; a common theme is that diagnosis of sarcopenia should include identification of both low muscle mass and poor muscle function, indicated by either low muscle strength or impaired physical performance, such as slow gait speed. The European Working Group on Sarcopenia in Older People (EWGSOP) consensus outlined an algorithm to aid the screening and diagnosis of sarcopenia. Box 2.4 shows the diagnostic criteria. Patients with gait speeds of 0.8 m/s or less should then undergo a second performance assessment, such as grip strength. Those meeting the criteria for low grip strength should be assessed by DXA (Chap. 1) or bioelectrical impedance analysis (BIA) to confirm the presence or absence of sarcopenia .
Box 2.4: Diagnostic Criteria for Sarcopenia
Sarcopenia should be considered in patients with presence of criteria 1 plus criteria 2 or 3:
Criteria 1: Low muscle mass
DXA >2 SD below mean of the younger adults:
Men <7.26 kg/m2
Women <5.5 kg/m2
Lowest 20% of the distribution of appendicular skeletal mass (ASM) in a normative population (aged 65 years and older)
Men <7.23 kg/m2
Women <5.67 kg/m2
Lowest 20% distribution of the residual of ASM adjusting for height and fat mass
BIA >2 SD below mean (SMI) of the younger adults
Men <8.87 kg/m2
Women <6.42 kg/m2
Criteria 2: Low grip strength
Men: <30 kg
Women: <20 kg
Criteria 3: Low physical performance
2.3.2 The Clinical Consequences of Sarcopenia
Osteoporosis predicts the future risk of fracture; and sarcopenia is a powerful predictor of future disability . Reduced muscle mass and strength are also associated with lower bone mineral density [47, 48], consistent with the “mechanostat” theory of bone loss due to reduced forces of muscle on bone . In fact, sarcopenia may contribute to falls and, as a consequence, increase fracture risk [50, 51]. Hence, not surprisingly, there is evidence that low muscle mass and strength are associated with fractures . Several studies have confirmed associations between low muscle mass, future functional decline and physical disability . Physical inactivity or decreased physical activity is part of the underlying mechanisms of sarcopenia, so physical activity is important in reversing or modifying it. Several interventions have been proposed for the treatment of this loss of muscle and strength, but exercise is central. Sarcopenia has also been linked to higher hospitalisation rates, increased morbidity and mortality [52, 53]. Sarcopenia may also be associated with metabolic and cardiovascular diseases such as diabetes, dyslipidaemia and hypertension .
2.3.3 Interventions to Prevent Sarcopenia
It is better to prevent progressive loss of skeletal muscle mass, strength and function rather than try to restore it later, so preventive strategies should be initiated early, before loss of skeletal muscle mass and strength occurs.
Exercise interventions have the most significant improvement in sarcopenia. The benefits of physical activity in the elderly population include lower mortality and functional independence (Chap. 6). There are four specific categories of recommended exercise: (1) aerobic exercise, (2) progressive resistance exercise, (3) flexibility exercise and (4) balance training .
Nutrition is also important in preventing and reversing sarcopenia (Chap. 7). Increasing age is associated with reduced appetite and early satiety, resulting in many older people failing to meet the recommended daily dietary allowance (RDA) for protein, which has important implications for skeletal muscles . Older adults will require higher dietary protein (up to 1.2 g/kg/day) to counteract age-related changes in protein metabolism and higher catabolic state associated with chronic or acute diseases .
It is the combination of exercise and nutrition interventions that is the key to preventing, treating and slowing down the progression of sarcopenia . Pharmaceutical agents are under investigation but with no current proven benefit. Pharmacological agents such as myostatin inhibitors, testosterone, angiotensin-converting enzyme inhibitors and ghrelin-modulating agents are being investigated to treat sarcopenia, but there is inadequate evidence to support their use. Low serum vitamin D levels are associated with reduced muscle strength, and it has also been demonstrated that a dose-response relationship exists between serum levels and muscle health. If serum levels are low, vitamin D should be replaced with replenishment dosages ranging from 700 to 1000 IU/day .
Box 2.5: Multiple Factors That Contribute Collectively to Frailty, Sarcopenia and Falls
• Social factors including social isolation, living alone
• Lack of access to transport
• Elder abuse
• Poverty and food insecurity
• Failure to provide for ethnic food preference
• Inability to prepare and cook meals or to feed self
• Inability to shop
• Thyroid disease
• Cardiac failure
• Gastrointestinal disease affecting absorption: anorexia (antibiotics/digoxin), early satiety (anticholinergic drugs), reduced feeding ability (such as sedatives/psychotropics), dysphagia (NSAIDs), constipation (opiates/diuretics), diarrhoea (laxatives/antibiotics), hypermetabolism (thyroxin)
• Sensory impairment—vision/hearing
• Oral problem, e.g. poorly fitting dentures
• Swallowing problem/dysphagia, thickened diet
• Poorly managed pain or constipation
More difficult to treat:
• Medical factors
• Loss of taste and smell, restricted diets
• Mood—depression, paranoia
Implementing interventions for frailty and sarcopenia has several challenges and barriers. A systematic review demonstrated that older people believe that exercise is unnecessary or, even, potentially harmful . Others recognise the benefits of exercise but report a range of barriers to participation in exercise interventions. Raising awareness is important to enhance exercise participation among older people and to prevent sarcopenia.
Another barrier that needs to be considered in planning long-term strategies to prevent and treat sarcopenia in older people is the financial ability to attend exercise programmes . Factors such as access to food, finances and social isolation may all impact on an older person’s ability to obtain optimal food intake.