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The 83-year-old woman is too weak to climb the stairs to her bedroom and remains on the first floor of her house. With her gradual loss of arm and leg strength, even standing up from the toilet is taxing. Because her balance is poor, she must hold onto furniture when she walks.
This woman is at high risk for falls, fractures, disability and loss of independence.1 She is among the about one in five Americans over age 65 who have a condition called sarcopenia.2
Sarcopenia is the loss of skeletal muscle mass and strength, leading to muscle weakness. The term sarcopenia (from the Greek “sarx,” or flesh, and “penia,” or loss) was first used by researcher Irwin Rosenberg in 1989 to refer to age-related loss of skeletal muscle mass.3 Since then, sarcopenia has been defined as “the loss of skeletal muscle and strength that occurs with advancing age.”1
But the lack of an accepted definition of sarcopenia has hampered the ability to develop consensus diagnostic criteria, International Classification of Diseases 9th Revision (ICD-9) codes or treatment guidelines.1 The lack of diagnostic criteria also hinders possible future management options.4
In an effort to remedy this, in 2010 the European Working Group on Sarcopenia in Older People recommended using the presence of low muscle mass and low muscle function (strength or performance) for the diagnosis. The working group suggested categories: “primary” (or age-related), when the only evident cause is aging; “secondary,” when one or more other causes are evident; and “geriatric syndrome,” when there are many causes, usually including frailty, immobility and weakness. The working group also defined conceptual stages as “presarcopenia,” low muscle mass without low muscle strength; “sarcopenia,” low muscle mass plus low muscle strength or low physical performance; and “severe sarcopenia,” when all three (low muscle mass, low muscle strength and low physical performance) are involved.1 Sarcopenia affects an estimated 50 million people worldwide; as many as 50% of people over 80 have the condition.1,4
Therapists are likely to encounter people with sarcopenia in hospitals after a fall, as well as in nursing homes, assisted-living facilities, public health wellness programs or even in their own homes. Therapists must be able to address this common problem by identifying causes and consequences and by teaching preventive measures to improve quality of life.
As people age, muscle mass (the number and size of muscle fibers) declines, and body fat increases. Between the ages of 30 and 60, the average adult can lose about a half a pound of muscle and gain about 1 pound of fat every year.5 More than 50% of community-dwelling Americans over 80 have a condition called sarcopenic obesity, defined as the coexistence of sarcopenia and obesity.6
After age 50, the rate of muscle loss is estimated to be 1% or 2% annually, along with declines in strength of 1.5% a year, increasing to 3% a year after 60. These declines result in a decrease in total muscle area of 40% between ages 20 and 60, and even higher in sedentary people.5 About 50% of a person’s total muscle mass has vanished by age 75.7 This results in reduced strength and exercise tolerance, weakness and fatigue, and a reduced ability to perform activities of daily living. Those with the greatest loss in lean body mass are at the greatest risk of falls.4,7
Loss of muscle mass is also a strong predictor of mortality in later life. In a study of 715 men 50 or older, mortality was higher in those with a faster loss of skeletal muscles of the limbs.8 Weak grip strength, poor function and low muscle density, but not muscle size or lean mass, were also associated with greater risk of hospitalization in a study of 3,011 adults ages 70 to 80. Participants with the weakest grip strength were at the greatest risk.2 Evidence was also found of an association between grip strength, walking speed, chair rising and standing balance times and mortality. Those performing less well in those tests were at higher risk of death.9 (Level C)
Sarcopenia also affects cardiopulmonary fitness. In a study of 275 community-dwelling older adults, cardiopulmonary fitness was significantly lower in those with sarcopenia than in those with normal skeletal muscle mass.10 (Level B)
Forces Behind Sarcopenia
Factors involved in the development of sarcopenia include age-related loss of muscle mass and fibers, a sedentary lifestyle, poor nutrition, adverse glucose metabolism and insulin resistance, and altered hormonal levels of growth hormone and testosterone.4,6 There is also some evidence linking low birth weight with lower muscle mass and strength in later life.11
The decline in food intake associated with “anorexia of aging”12 (age-associated physiologic reduction in appetite and food intake) is a risk factor in the development and progression of sarcopenia.5 Sarcopenia is also a component of nutritional frailty, the disability that occurs due to rapid, unintentional loss of body weight in old age.12 Malnutrition due to anorexia of aging leads to loss of lean muscle mass and muscle strength.
Fifteen percent of people older than 60 eat less than 75% of the recommended daily allowance for protein, and almost 40% of those over 70 do not meet the recommended dietary allowance of 0.8 g/kg/day of protein.4,5 Although poor overall nutrition may play a role in sarcopenia, low protein intake appears to be a significant problem for older adults.5
Older adults are at increased risk of developing a vitamin D deficiency. As people age, the skin is less able to synthesize vitamin D, and the kidneys are less able to convert vitamin D to the hormone form.5 A study of 9,704 women 65 and older showed that low levels of vitamin D among women who were not frail were associated with an increased risk of frailty as defined by sarcopenia, weakness, exhaustion, slowness and low physical activity.13 (Level B)
A sedentary lifestyle plays a significant role in the decline of muscle mass and function with aging. Only about 20% to 25% of older adults meet the recommended exercise goal of 30 minutes five times a week, which can include walking or activities such as gardening.7
Periods of physical inactivity, such as bed rest during an illness, can worsen loss of muscle mass and strength as well as cause stiffness of muscles, ligaments and tendons, leading to a contracture.7 Complete bed rest can cause a young adult to lose about 1% of muscle mass per day; older adults may lose up to 5% per day as a result of decreases in growth hormone. Muscle mass loss is greatest in the antigravity muscles (those used to sit up, stand up and pull up) and can require up to two weeks of reconditioning for each day of absolute bed rest.7 Patients should avoid extended bed rest when possible to prevent muscle weakness and joint stiffness.
Because muscle weakness can be a symptom of many medical disorders, careful subjective and objective assessments are essential to identify possible causes of muscle weakness other than sarcopenia. The basic elements of the assessment should include information on the following:
1. Height and weight: Question any weight loss or gain. Height and weight data help identify obesity or drastic weight loss. One way to determine whether a person’s weight is healthy is to calculate the body mass index.14 BMI is an indicator of body fatness that is calculated based on a person’s height and weight. A BMI of less than 18.5 is considered to be underweight. A BMI of 18.5 to 24.9 is in a healthy weight range, a BMI of 25 to 29.9 is overweight, and a BMI of 30 or higher is obese. BMI is used as a screening tool to identify possible weight problems for adults, but it is not diagnostic of the body fatness or health of an individual.
2. Nutrition: What is the typical daily dietary intake? Is the dietary intake sufficient to supply the essential amounts of carbohydrates, fat, protein, vitamins, minerals and calories? Is the older adult drinking enough water? Dehydration can cause weakness.
3. Lifestyle: Obtain information about activity and rest patterns, both past and present. What does the patient do to stay fit?
4. Ability to perform ADLs: What kind and amount of help does the patient need with bathing, dressing, walking and preparing and eating meals?
5. Medications: Older patients are more prone to drug toxicities and adverse effects. Review all medications with the patient. Prolonged use of medications such as steroids, potassium-depleting drugs and colchicine (an antigout agent) can precipitate progressive muscle weakness.15 Statins or other drugs to reduce cholesterol may cause myalgia and muscle weakness in some people.16
Excessive use of muscle relaxants, digoxin, alcohol or recreational drugs can contribute to muscle weakness.15 Many medications, medication-medication interactions and medication-food interactions can affect the absorption of nutrients, including those needed to maintain and repair muscle tissue. Some medications may reduce appetite, thus compromising nutritional intake and leading to anorexia of aging and malnutrition.
6. Medical and surgical history: Obtain a history of chronic or muscle-debilitating diseases and illnesses, total joint replacement and trauma. Does the patient have a history of anemia, connective tissue disease, diabetes mellitus, renal disease or thyroid disease? Hematologic conditions, such as low hematocrit and hemoglobin levels, cause inadequate oxygen supply to muscles, leading to decreased muscle strength.17 Chronic pain from recent hip or knee replacement surgery and chronic diseases such as rheumatoid arthritis and osteoarthritis can cause muscle weakness in older patients if they lack muscle use. Progressive symmetrical muscle weakness can occur in osteomalacia (abnormal softening of bone) and osteoporosis, which is often caused by a deficiency of phosphorus, calcium or vitamin D. Muscle weakness in elderly patients often affects muscles of the pelvis and the quadriceps. Muscle weakness and atrophy can result from a herniated disk after prolonged pressure on the peripheral nerve roots. Typically, the patient complains of back pain in addition to muscle weakness. Distal muscle weakness can also be a sign of peripheral neuropathy, which has many causes. Muscle weakness may also be a symptom of multiple sclerosis.15 Once you obtain information from the patient and family, ask the following questions to further characterize the muscle weakness: Was the onset gradual or sudden? Is the muscle weakness progressive, intermittent or stable? Is it unilateral or bilateral? Is it generalized or localized to one muscle area? Sudden onset of muscle weakness is often associated with transient ischemic attacks or stroke, which have to be ruled out. The red flags for TIA or stroke are sudden weakness on one side of the body or both, loss of coordination, unexplained dizziness, changes in speech or a sudden dimness or loss of vision, particularly in one eye. These findings require immediate attention.
Localized weakness can be due to a spinal cord or brain lesion, for example, in patients with MS or cervical or lumbar spinal stenosis.15
Symptoms such as numbness, muscle pain, twitching, change in sensation and heat intolerance provide valuable information. For example, a loss of sensation in the feet can lead a therapist to suspect peripheral neuropathy associated with long-term poorly managed diabetes or folate deficiency. After assessing weight and height, observe how the patient walks. Unsteady gait can be due to weakened muscles. Observe whether the patient favors one side. Does the patient use a cane or a walker? The muscle assessment includes observing and inspecting muscle bulk and tone. Look for atrophy of the muscle, which could be caused by disrupted nerve innervation to a damaged muscle or by prolonged immobility. Assess the patient for signs of inflammatory arthritis, such as painful, red and swollen joints.7
Because muscle weakness can be a symptom of many disorders, additional tests will help rule out treatable conditions that in many cases could precipitate or aggravate sarcopenia. An albumin level below 3.5 g/dL raises concern for malnutrition.18 Helpful blood tests to consider include those for thyroid-stimulating hormone, CBC and blood glucose level.17 Measurement of serum electrolyte and bicarbonate levels can rule out acidosis or alkalosis; this is especially important if the patient complains of cramps and muscle pain with the muscle weakness.19
Several methods can be used to determine the body’s muscle mass, strength and physical performance related to sarcopenia. These include imaging techniques and observational assessments of physical function.1
Imaging techniques that can estimate muscle mass or lean body mass include CT scan, MRI and dual energy X-ray absorptiometry, or DXA. CT and MRI are precise imaging systems that can separate fat from other soft tissues of the body, making them good methods for estimating muscle mass. DXA is good for distinguishing fat, bone mineral and lean tissues.1
Observational assessments of physical function include measuring handgrip strength and knee flexion/extension. Handgrip strength is strongly related to leg strength. Isometric (muscular contraction against resistance) handgrip strength can be measured using a hand-held dynamometer, a portable device that gives an objective measurement of strength during manual muscle testing. Low handgrip strength is an indicator of poor mobility and possible negative outcomes.1
Knee flexion/extension is measured by applying force to the ankle with the person seated in a straight-back chair, the lower leg unsupported and the knee flexed to 90 degrees.1 The Short Physical Performance Battery, an evaluation of balance, gait, strength and endurance, determines a person’s ability to stand with the feet together in side-by-side, semi-tandem and tandem (one foot behind the other, toe to heel) positions, time to walk 8 feet and time to rise from a chair and return to the seated position five times.1 The “timed get up and go,” an assessment of balance, requires the person to stand up from a chair, walk a short distance, turn around, return and sit down again. It is scored on a five-point scale.1
Calculations based on mid-upper arm circumference and skin fold thickness have been used in the past to estimate muscle mass in older people. But age-related changes in fat deposits and loss of skin elasticity contribute to errors of estimation, and such calculations are not recommended to diagnose sarcopenia.1
Recommendations from the Society for Sarcopenia, Cachexia and Wasting Disease for the prevention and management of sarcopenia include resistance exercise and aerobic exercise in combination with adequate protein and energy intake.20 (Level C) But many older adults find it difficult to maintain a balanced diet. A consultation with a registered dietitian to obtain a diet history and develop a plan for daily food intake is a necessary part of the evaluation, prevention and treatment of sarcopenia.
Although the current daily dietary protein intake recommended for adults is 0.8 g per kilogram of body weight, evidence exists that an intake of 1.2 g/kg to 1.5 g/kg of protein daily can prevent sarcopenia. Some studies show that it is more important to eat a sufficient amount of high-quality protein (25 g to 30 g) with each meal rather than one large amount.5 But consuming carbohydrates in a meal with protein may prevent muscle protein synthesis because of the effects of insulin resistance. This evidence suggests that high-quality protein should be eaten in smaller quantities, but not in the same meal with carbohydrates.5
Protein in food is made up of amino acids. Exercise stimulates amino acid metabolism, but just six amino acids affect skeletal muscle.20 One of the six essential amino acids, leucine, is known to especially increase the metabolism of protein and reduce protein breakdown.20 Leucine-rich foods include legumes, such as soybeans, cowpeas and lentils; nuts; brown rice; and animal products, such as beef and fish. Amino acid supplements without leucine may not stimulate protein synthesis.5
Omega-3 fatty acids may also be useful in preventing and treating sarcopenia. One study showed that omega-3 fatty acids were able to stimulate muscle protein synthesis in older adults.21 Although impaired protein digestion and absorption is typical in sarcopenia, the digestion and absorption of dietary protein is not impaired after exercise. Therefore, exercising before consuming protein permits more of the dietary protein-derived amino acids to be used for muscle protein synthesis.22
Fruits and vegetables rich in potassium may help preserve muscle mass, a study of 384 men and women over 65 showed. Protein and cereal grains are metabolized to acidic residues, mainly sulfuric acid, but fruits and vegetables are metabolized to alkaline residues, mainly potassium bicarbonate.23 Metabolic acidosis in diets of mostly protein and cereal grains may promote muscle wasting in older adults, but alkaline-producing fruits and vegetables rich in potassium may help preserve muscle mass.23 The acid-base balance of food in the diet is based on the acidic or alkaline residues a food produces in the body, not on whether the food is alkaline or acidic itself. An example is grapefruit: The fruit is acidic, but in the body it is metabolized to alkaline residues.24
Recent information about vitamin D shows that older people with low vitamin D levels should take supplements to combat sarcopenia, functional decline and the risk of falls. Vitamin D supplements are available as D2 in the form of ergocalciferol and D3 in the form of cholecalciferol.5 The best food sources of vitamin D are salmon, tuna, mackerel and fish liver oils. Small amounts of vitamin D are found in beef liver, cheese and egg yolks.5
Physical exercise, specifically muscle resistance training (training with weights), helps preserve or even increase lean body mass and strength. Care for hospitalized elderly patients should include an early physical therapy referral. The major muscles required for sitting up, standing up and pulling up are crucial for performing ADLs. An exercise plan tailored to strengthening large weight-bearing and supporting muscles benefits all older adults.
People who are physically active at least four hours a week live longer and better. That is the verdict of an 18-year-study that followed 1,861 older adults.25 The study showed a significant survival benefit associated with beginning physical activity between ages 70 and 85.25 The physical activity included walking as well as vigorous exercise.25 (Level B)
Muscle resistance training is especially effective for improving strength among older adults, especially with higher-intensity training, according to 47 studies representing 1,079 participants.26 (Level B) But sustainability could limit its use as a therapeutic approach. Older adults required more intense workouts than the young to maintain the muscle bulk they gained during progressive resistance training, but their gains in strength remained.27
The StrongWomen Program is an evidence-based, community-based, muscle-resistance training program. It was developed to help women 40 and older maintain their strength, function and independence. Program leaders receive training at the StrongWomen Workshop, where they receive the StrongWomen Tool Kit and get support to establish the program in their communities.28
Drugs such as growth hormones and testosterone have been suggested as a means to build muscle mass in older adults with sarcopenia. Although levels of growth hormone decrease with aging, growth-hormone supplementation increases muscle strength to only a small degree unless accompanied by muscle resistance training. Higher mortality rates are associated with elevated levels of growth hormone in middle-aged people. In addition, many adverse effects are associated with supplementation including arthralgias, carpal tunnel syndrome, glucose intolerance, fluid retention, gynecomastia, headaches and lethargy. The literature suggests that growth-hormone supplementation should be used only as replacement therapy for patients with a documented deficiency or for patients with muscle atrophy due to AIDS.7
One study showed that frail elderly men with low to borderline-low testosterone may benefit from testosterone treatment for six months to prevent age-related loss of leg strength and improve their quality of life and physical function.29 (Level A)
Act Now, Be Strong Later
Older adults should not accept sarcopenia as a necessary part of aging. The therapist’s role includes promoting independence and teaching older patients, their families and the public the consequences of immobility. Maintaining a diet with enough calcium, vitamin D, protein and calories and performing consistent weight-bearing exercises of the type outlined in the book Strong Women Stay Young can help older adults maintain strength and deter sarcopenia. Resistance exercise, even for frail elderly nursing home residents, can prevent falls and improve their quality of life.
For Further Reading
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