"Muscle" cannot be lost, the key to preventing "muscle" is...

As the saying goes, “A slim body in old age is worth more than money”, does “being slim in old age” mean “living longer in old age”?

In fact, this is not the case. Being thin often means muscle attenuation and strength weakening. When the limbs become soft and thin, and fat accumulates in the waist and abdomen, the body will become more and more fatigued, and you often cannot walk or lift things. The most troublesome thing is that you will get sick more and more. At this time, you must be alert to the health threat "muscle" - sarcopenia.

So what is sarcopenia, why does it occur, and how can it be treated and prevented?

What is sarcopenia?

Sarcopenia, also known as "skeletal muscle aging" or "sarcopenia" in clinical practice, refers to the decrease in skeletal muscle mass and muscle strength caused by aging. The prevalence rate is 8.9% to 38.8%. It is more common in men than in women, and the age of onset is more common in people over 60 years old, and the prevalence rate increases significantly with age.

The clinical manifestations are often lacking in specificity, and general symptoms include weakness, thin and weak limbs, easy falls, slow gait, difficulty walking, etc.

How is sarcopenia caused?

Primary factors

Aging causes a decline in the body's hormone levels (testosterone, estrogen, growth hormone, IGF-1), which reduces muscle protein synthesis, reduces the number of α motor neurons, attenuates type II muscle fibers, causes mitochondrial dysfunction and oxidative damage, increases in skeletal muscle cell apoptosis, reduces the number of satellite cells and their regenerative capacity, and increases in inflammatory cytokines.

Secondary factors

① Malnutrition

Insufficient dietary intake of energy, protein and vitamins, improper weight loss, etc., prompt the body to mobilize muscle protein reserves, reduce the muscle synthesis rate, increase the decomposition rate, and lead to muscle atrophy.

②Disease status

Chronic inflammatory diseases, tumors, endocrine diseases, or chronic heart, lung, kidney and other diseases will accelerate the decomposition and consumption of protein, the catabolism of muscle, and cause muscle loss.

③ Unhealthy lifestyle

Lack of exercise: Long-term bed rest, immobilization, sitting for long periods of time, and too little activity can lead to insulin resistance and accelerate muscle loss.

Alcoholism: Long-term alcohol intake can lead to atrophy of type II muscle fibers (fast twitch).

Smoking: Cigarettes reduce protein synthesis and accelerate protein degradation.

What are the dangers of sarcopenia?

Decreased ability to move

As muscles decrease and strength declines, people will feel weak and have difficulty completing daily activities such as sitting, walking, lifting objects, and climbing. They will gradually develop symptoms such as unsteady gait, difficulty getting out of bed, and inability to stand upright.

Increased risk of trauma

Sarcopenia often coexists with osteoporosis. Muscle attenuation can lead to poor movement and balance abilities, making falls and fractures very likely to occur.

Poor ability to resist and cope with stressful events

A small adverse event can produce a domino effect. Elderly people with sarcopenia are prone to falls, which lead to fractures after falls. They need to be hospitalized for treatment, and limb immobilization during and after hospitalization causes further muscle atrophy and loss of physical function in the elderly. This not only increases the care burden and medical expenses of society and families, but also seriously affects the quality of life and even shortens the life span of the elderly.

Reduced immunity

A 10% decrease in muscle mass will lead to decreased immune function and increased risk of infection; a 20% decrease in muscle mass will lead to weakness, decreased ability to live in daily life, delayed wound healing and infection; a 30% decrease in muscle mass will make it difficult to sit up independently, and pressure sores will easily develop, which may even cause disability; a 40% decrease in muscle mass will significantly increase the risk of death, such as death from pneumonia.

Endocrine and metabolic disorders

Muscle loss will lead to a decrease in the body's insulin sensitivity and cause insulin resistance; at the same time, muscle loss will affect the body's lipid balance, reduce the basal metabolic rate, and then cause fat accumulation and metabolic disorders.

How to quickly screen for sarcopenia?

Calf circumference

Use a non-elastic tape measure to measure the maximum circumference of the bilateral calves. If it is less than 34 cm for men and less than 33 cm for women, it is considered abnormal.

If you don't have a tape measure, you can use the "ring test" to test, that is, use the thumbs and index fingers of both hands to surround the thickest part of the non-dominant calf. If the circumference formed by the hands is just right or larger than the calf, then the risk of sarcopenia is greater.

Do the questionnaire

What tests are needed for sarcopenia?

Muscle mass assessment

① Dual-energy X-ray absorptiometry (DXA) is widely used and is the gold standard for measuring muscle mass. DXA <7.0 kg/m2 for men and <5.4 kg/m2 for women is considered abnormal.

② Bioelectrical impedance analysis (BIA) is simple and convenient to operate and is often used for large-scale population screening. BIA is abnormal when male <7.0 kg/m2 and female <5.7 kg/m2.

Muscle strength assessment

Grip dynamometer is the most commonly used method to assess muscle strength and is also the preferred indicator for assessment and diagnosis. It is abnormal for men <28kg and women <18kg.

Physical function assessment

The 6m walking speed is easy to measure and is the most commonly used method to assess physical function. The faster the speed, the higher the physical fitness level. A walking speed of less than 1.0 m/s is abnormal.

If the test results are 1+2, 1+3, or 1+2+3, it is diagnosed as sarcopenia.

Treatment of Sarcopenia

01Nutritional support

The main purpose is to consume sufficient energy and protein to promote muscle protein synthesis, increase and maintain muscle mass.

02Exercise intervention

Exercise can significantly increase muscle mass and strength.

① Resistance exercise (such as pulling elastic bands, lifting dumbbells or mineral water bottles, etc.) is the basis and core part of exercise intervention. It is characterized by gradually increasing exercise intensity. By increasing the cross-sectional area of ​​type I and type II muscle fibers, it enhances the muscle mass of the whole body and improves physical function and walking speed.

② Aerobic exercise (such as jogging, brisk walking, swimming, etc.) can improve muscle strength and overall muscle coordination by improving mitochondrial metabolism and expression, improve cardiopulmonary function and mobility, improve endurance, reduce the risk of metabolic diseases, reduce body fat percentage, improve immunity, and enhance the body's adaptability.

③Balance training can help patients maintain body stability in daily life or activities and reduce the risk of falling.

03Drug treatment

There are currently no drugs for sarcopenia.

Prevention of Sarcopenia

1. Pay attention to dietary nutrition

Routinely conduct nutritional screening for the elderly. Avoid high-fat and high-sugar diets. Take 1.2g/(kg.d) of leucine-rich protein, supplement vitamin D appropriately, eat more dark vegetables, fruits and beans, ensure adequate daily energy intake, and prevent malnutrition.

2. Develop a healthy lifestyle

Pay attention to exercise, avoid absolute rest or sitting for long periods of time, exercise reasonably, step by step, and focus on not feeling tired; quit smoking and drinking, maintain a good attitude, spend more time with the elderly, and avoid depression.

3. Weight Management

Maintain an appropriate weight, avoid being overweight or underweight or having large fluctuations. A weight loss of no more than 5% within six months is appropriate, and keep the body mass index (BMI) between 20 and 24 kg/m2.

4. Pay attention to abnormalities

If you experience abnormal phenomena such as deterioration of cardiopulmonary function, decreased mobility, and fatigue, do not be careless and go to the hospital for examination as soon as possible to avoid delaying the condition.

5. Strengthen inspection

It is recommended that people over 60 years old should strengthen their gait speed test → grip strength assessment → muscle mass measurement when they have physical examinations or fall repeatedly, so as to achieve early detection and early treatment.

6 Intervention of inflammatory factors

Chronic diseases such as chronic heart failure and chronic obstructive pulmonary disease are often accompanied by inflammatory responses and enhanced protein catabolism, so the primary diseases should be actively treated and controlled.

References

1. Cui Hua, Wang Zhaohui, Wu Jianqing, et al. Chinese expert consensus on prevention and control of sarcopenia in the elderly (2023)[J]. Chinese Journal of Geriatrics, 2023, 42(2): 144-153. DOI: 10.3760/cma.j.issn.0254-9026.2023.02.002.

2. Yu Pulin, Gao Chao, Zhou Baiyu, et al. Chinese expert consensus on core information for preventing sarcopenia in the elderly (2021)[J]. Chinese Journal of Geriatrics, 2021, 40(8): 953-954. DOI: 10.3760/cma.j.issn.0254-9026.2021.08.002.

Author: Yan Xuehua, head nurse, Guangzhou Medical University Brain Hospital

Reviewer: Yang Jian, Chief Physician, Vice Chairman of the Geriatric Rehabilitation Committee of the Chinese Rehabilitation Medicine Association

Illustration: Li Chuan, Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine