What is Sarcopenia?
Sarcopenia is the loss of skeletal muscle mass, strength and function associated with the aging process. Sarcopenia is an important clinical problem that impacts millions of older adults. Till the age of 30 the muscles are in peak condition and grow larger and stronger, after which there is a gradual deterioration.
From 30 to 80 years of age, there is an estimated 30% reduction in muscle mass and an approximately 20% decline in the cross-sectional area of muscles. This is due to a decline in muscle fiber size and well as number of muscle fibers. This can contribute to mobility issues, osteoporosis, falls, fractures, frailty, loss of physical function and independence.
Skeletal muscle and bone mass are the principal components of lean body mass to decline with age. The term sarcopenia also termed "poverty of flesh" is derived from the Greek words sarx meaning "flesh" and penia meaning "poverty".
Muscle loss and others signs associated with aging are inevitable processes. A person can lose as much as 3% to 5% of their muscle mass each decade after 30 years of age. Since muscle mass accounts for up to 60% of the body mass, loss of muscle reflects in an uneven balance, gait and overall ability to perform daily tasks.
Sarcopenia is mostly seen in the physically inactive or sick people, but it is also evident in individuals who remain physically active throughout their lives. People who lead a sedentary lifestyle are most likely to experience pronounced sarcopenia as they age. Being a couch potato is a sure way to suffer serious loss of muscle mass late in life.
Sarcopenia is also a key component of the frailty syndrome and cachexia. The frailty syndrome is an unintentional weight and muscle loss that leaves a person vulnerable to falls, exhaustion, fractures, and declines in grip strength, gait speed, and activity.
Cachexia or wasting syndrome is a condition that appears in patients with certain chronic and terminal illnesses. However, malaise or a feeling of discomfort is a key feature in such people.
There is a lot of global interest in research for ways to slow down the aging process, especially in relation to loss of muscle mass and strength. Studies have shown that muscle function, rather than mass, is associated with a high mortality risk. Fortunately, sarcopenia is partly reversible with appropriate exercise and diet interventions.
- It is estimated that sarcopenia affects 30% of people over the age of 60 and more than 50% of those over the age of 80.
- Between the ages of 30 and 60, the average adult gains 1 lb of weight and loses 1/2 lb of muscle yearly, a total gain of 30 lbs of fat and a loss of 15 lbs of muscle.
- After the age of 70, muscle loss increases to 15% per decade.
- People who have sarcopenic obesity seem to have worse outcomes than those who are not obese.
- Estimates indicate that 20% of older adults in the United States are functionally disabled, and the risk of disability is 1.5 to 4.6 times higher in older adults with sarcopenia than in those with normal muscle.
- Half of all accidental deaths among people over the age of 65 with sarcopenia are related to falls.
- The economic burden of healthcare related expenditures for sarcopenia in the United States is estimated to be $18.5 billion annually.
- Aging which is an inevitable process.
- Decreased physical activity. As we age we become more accustomed to comforts and our physical activity reduces considerably. This results not only in muscle mass reduction but also in increase of body fat, both of which puts extra pressure on the weak muscles.
- Increased incidence of chronic diseases in old age leads to pain and fatigue that also results in older adults becoming less active.
- Declining testosterone hormone levels. Testosterone plays a key role in increasing and maintaining muscle mass.
- Decreased protein synthesis. Loss of skeletal muscle protein results from an imbalance between the rate of muscle protein synthesis and degradation.
- Obesity and fat infiltration into skeletal muscle plays an important role in the development of sarcopenia.
- Declining levels of growth hormone.
- Nutritional deficiencies especially of dietary protein and vitamin D.
- Chronic inflammatory conditions such as rheumatoid arthritis, kidney disease, and autoimmune diseases.
- Insulin like growth factor 1 deficiency. This hormone plays an important role in the growth, mineralization of bone and increase in muscle mass.
- Low birth weight has also been found to a contributing factor in developing reduced muscle mass and strength in adult life.
- Motor unit restructuring / decreases in the number of neuromuscular junctions. The neuromuscular junction is comprised of motor units each of which consists of a motor neuron and all the muscle fibers that it connects to and stimulates. A motor unit is responsible for sending signals from the brain to the muscles to initiate movement. Motor unit restructuring refers to the ongoing changes in number and function of spinal cord motor units.
- Decrease in the size of muscle or muscle atrophy.
- Weakness and reduction of muscle strength. This loss of muscle strength places increased stress on joints and can predispose to arthritis or falls.
- Decreased ability to turn protein into energy.
- Poor muscle balance resulting in chronic injuries, fractures, aches and pains.
- Difficulty in getting out of a chair or ascending stairs.
- Slow walking speed.
- Reduction in nerve cells responsible for sending signals from the brain to stimulate the muscles.
- Lower concentrations of growth hormone, testosterone, and insulin like growth factor.
- Low vitamin D levels in blood [< 50 nmol/liter].
- Increased risk of disability, hospitalization and mortality.
- Poor wound healing.
- Decreased insulin resistance.
A person is considered to have sarcopenia if they have low muscle mass and either low gait speed or low muscular strength. If they have all three conditions, it is a case of severe sarcopenia.. The diagnostic measures are:
- DXA (dual energy X ray absorptiometry) proposed by Baumgartner et alis the standard technique to distinguish fat, bone mineral and lean tissues. The lean body mass of the affected person is compared to a normal reference population. Having a low muscle mass that is more than 2 standard deviations below the mean measured in young adults aged 18–39 years and who belong to the same sex and ethnic background is an indication of sarcopenia.
- Measuring walking speed. Average gait speeds for older adults range from 0.60 to 1.45 meter/second [m/sec]. A gait speed < 0.8 m/sec in the 4 minute walking test is considered diagnostic for sarcopenia.
- Handgrip strength is a good measure of muscle strength. Grip strength less than 30 kg in males and less than 20 kg in females is indicative of sarcopenia.
- The risk of disability is 1.5 to 4.6 times higher in older adults with sarcopenia.
- Malnutrition. This can result from many factors, including illness, injury, and insufficient or erratic food intake. This leads to further breakdown of skeletal muscle.
- Increased risk of illness and infection.
- Prolonged recovery from surgery, illness, and injury.
- Increased risk of mortality.
- Exercise is the best treatment for sarcopenia. Regular exercising can prevent or delay onset of sarcopenia. Resistance exercise such as lifting weights and using resistance bands have been shown to decrease frailty, improve muscle strength and prevent osteoporosis. Endurance exercises such as swimming and brisk walking improve the cardiovascular and circulatory system. Exercise is recommended on a daily basis, but a minimum of three times per week is vital.
- Increased protein intake. Studies recommend a total protein intake of 1 to 1.5 gm/kg/day. One study of adults over the age of 50 noted that 27% to 41% of women and 15% to 38% of men consumed less than the daily requirement of protein.
- Vitamin D supplementations in sarcopenic individuals to increase levels above 100 nmol/L. Low vitamin D levels are associated with low muscle strength.
- Testosterone therapy for men with low testosterone levels has been linked to increased muscle mass. However, it has not been associated with improved functional performance or a reduction in mortality. In addition, cardiac complications and prostate cancer are potential risks.
- Hormone replacement therapy [HRT] can increase lean body mass and prevent bone loss in menopausal women. But usage has shown increased risk of breast cancer and other serious health problems. Hence their usage is advised with caution.
- Growth hormone increases muscle protein synthesis and muscle mass, but does not lead to gains in strength and function in most studies. Its usage is controversial.
- By exercising regularly.
- By eating a diet rich in high-quality protein, fruits and vegetables, with reduced intake of cereal grain foods and fats. Include whey protein, which contains bio-identical amino acids as required by the body.
- Taking Vitamin D supplements to maintain levels between 40-65 ng/ml.
- Leucine supplements [an essential amino acid] to increase muscle protein synthesis.
- Intake of omega 3 fatty acids can provide a safe, simple and low-cost intervention to sarcopenia.
- Walston JD. Sarcopenia in older adults. Current opinion in rheumatology. 2012;24(6):623-627. doi:10.1097/BOR.0b013e328358d59b.
- Sarcopenia in older adults - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4066461/)
- Skeletal muscle loss: cachexia, sarcopenia, and inactivity - (http://ajcn.nutrition.org/content/91/4/1123S.full)
- What is sarcopenia? - (https://www.iofbonehealth.org/what-sarcopenia)
- Frailty syndrome: an overview - (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3964027/)
- Diagnosing Sarcopenia - (https://www.iofbonehealth.org/diagnosing-sarcopenia)
Latest Publications and Research on Sarcopenia
- Sarcopenia as a predictor of nutritional status and comorbidities in hospitalized patients with cancer: A cross-sectional study. - Published by PubMed
- Influence of the new EWGSOP2 consensus definition on studies involving (pre)sarcopenic older persons. Comment on «?Sarcopenia?» by Tournadre et al. Joint Bone Spine 2019;86(3):309-14. - Published by PubMed
- Inflammatory biomarkers of frailty. - Published by PubMed
- Automated body composition analysis of clinically acquired computed tomography scans using neural networks. - Published by PubMed
- Age-related degeneration of the lumbar paravertebral muscles: Systematic review and three-level meta-regression. - Published by PubMed
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