Sarcopenia
Summary:
Sarcopenia is the progressive loss of muscle mass and function, so there is less muscle and what is there is weak. It used to be seen only in the elderly or after serious illness, but modern lifestyle factors (sedentarism, poor diet) mean it is becoming more common in younger individuals. It increases the risk of falls and injury, as well as the risk of metabolic diseases such as diabetes.
In the context of weight management, we must be particularly aware of the possibility of sarcopenia in patients who do repeated diets (yoyo dieting) because a little muscle is lost with each diet attempt, but weight regain is typically just fat; the end result can be considerable muscle loss. Also, patients on a poor-quality diet, fad diets, or diets with insufficient protein are likely to lose muscle. When dieting to lose weight, it is essential to use programmes that ensure protection of muscle.
For detailed information on sarcopenia, please read on
(For sarcopenic obesity, see my blog article here.)
The Detail
What is sarcopenia?
Sarcopenia is a term derived from Greek, literally meaning “poverty of tissue”.
In medicine, the definition of sarcopenia was agreed in a 2010 European consensus document, which was updated in 2018 (See updated document)
Sarcopenia is a syndrome characterised by a progressive and generalised loss of muscle mass and strength, with an increased risk of physical disability, poor quality of life, and death.
Note that a diagnosis of sarcopenia requires us to assess not only muscle mass but also the strength and function of the remaining muscle. This is important from a treatment point of view, as our aim should be not only to increase muscle mass but also to improve performance.
Sarcopenia is now included in the International Classification of Diseases (ICD)-10, giving it recognition in the medical community as a disease. This may lead to health funding changes and encourages research and the development of new treatments.
Cachexia
Cachexia is defined as muscle wasting, with or without loss of fat, caused by an underlying disease. Whilst cachectic patients are sarcopenic by definition, the vast majority of sarcopenic individuals are not cachectic.
Frailty
Frailty is an age-related decline in multiple body systems, including muscle. It leads to an increased risk of falls and injury as well as a reduced ability to withstand stress (physical, metabolic, immunological). The concept goes beyond physical changes to include psychological, cognitive and social impairment.
What causes sarcopenia?
Sarcopenia is observed most commonly in the elderly and its prevalence increases considerably after the age of 70; however, it can be seen in younger individuals. In some cases, no cause other than ageing can be identified (“primary sarcopenia” or “age-related sarcopenia”), but the following possible causes must be considered:
Activity-related
Bed rest, sedentary lifestyle, zero gravity
Disease-related
Advanced organ disease (heart, lung, brain…), inflammatory diseases, cancer, endocrine diseases
Nutrition-related
Inadequate energy or protein intake. Malabsorption. Appetite suppressants. Yoyo dieting
Medication
Corticosteroids
Sarcopenia can develop rapidly, and even short periods of bed rest (less than a week) can produce a significant fall in muscle mass and muscle strength. Three to five weeks of bed rest can reduce muscle strength by 50%.
Why is sarcopenia important?
Sarcopenia directly impacts quality of life and increases the risk of falls, injury and mortality. The metabolic changes in the muscle affect how the body handles sugar and fat. These functional and metabolic problems can exacerbate coexisting diseases and significantly delay recovery from illness or injury.
Restoration of muscle strength and function is a slow process. In the elderly, it is often not possible to regain muscle mass, though it is very important to prevent any further loss and to improve the function of what muscle remains.
How is sarcopenia diagnosed?
Muscle mass:
- Body imaging techniques: The gold standards are magnetic resonance imaging and computed tomography, but these are expensive and not widely accessible. DEXA (dual-energy x-ray absorptiometry) is accepted as the gold standard in clinical practice.
- Bioelectrical impedance analysis: An inexpensive, reproducible test that has been validated in different ethnic groups. Devices are portable and some can even be used in bedridden patients.
- Total body potassium: The total body potassium can be used to assess fat and muscle, but it is a relatively costly and laborious method and is seldom used nowadays.
Muscle strength:
- Handgrip strength: This simple and inexpensive test performed using a hand dynamometer has been shown to correlate well with lower limb strength. Low handgrip strength is a better predictor of disability than low muscle mass.
- Knee flexion/extension: Measures strength and power, but special equipment is necessary and the test is rarely used in clinical practice.
Physical Performance:
- Short Physical Performance Battery: A series of tests used to assess balance, gait, strength and endurance in the clinic.
- Usual gait speed: Small changes in muscle function and strength can have marked effects on performance in frail adults. A study of walking speed measured on a 6-metre course has been found to correlate with adverse health events.
- Timed get-up-and-go test: The time to get up from a chair, walk a fixed distance, turn around and sit down again. This assesses balance and strength..
Treatment
First, reversible causes (especially medication) must be excluded or treated.
Treatment is multidisciplinary and focuses on nutrition and exercise. Special attention must be paid to possible alterations of intestinal absorption (decreased micronutrient and protein absorption in the elderly or in persons with certain intestinal diseases). A relatively high-protein diet is usually indicated, and vitamin D supplementation is recommended by many practitioners. Exercise must be tailored to the patient’s ability; muscle strength is slow to recover, and motivation can be difficult. Resistance exercise is important to increase strength and endurance.
Pharmacological treatment may occasionally be indicated, but the effects are still not fully defined. Medicines are only ever an adjunct to exercise and nutrition, never a substitute.
