Muscle Wasting: Causes and Symptoms, Diagnosis, Types of Muscle Wasting, and Life Expectancy

Over 600 muscles support and move the body. They are also involved in various organ functions.

Muscle wasting (ICD code: M62.5) generally refers to the loss of muscle mass. There are various causes for this, including, for example,

• bedridden status,
• injuries to the nervous system,
• metabolic disorders, and
• over 700 possible genetic disorders.

However, muscle wasting can also be congenital.

Muscular atrophy affects only a relatively small number of people. An estimated 50,000 to 300,000 people in Germany are affected by muscular atrophy.

The human muscular system © adimas / Fotolia

Muscle diseases and muscle wasting have not yet been fully researched scientifically.

About 800 forms of muscle diseases are now known. As a result, it has not yet been possible to develop tailored medications for the various forms of muscle wasting.

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Depending on the severity and context, the course of muscle wasting can vary greatly. Some people are hardly limited by this condition. Others may develop severe symptoms within a relatively short period of time. Premature death is also possible.

Muscular disorders progress in episodes, meaning they advance irregularly and at varying rates.

In the majority of cases, a cure is not possible, and spontaneous recovery does not occur naturally.

Muscle wasting due to lack of exercise

If muscles are not used, the body breaks them down because muscles require a lot of energy. Physical inactivity and bed rest therefore lead to the atrophy of many muscles. Seniors with an inactive lifestyle are particularly at risk for this type of muscle wasting.

This phenomenon is already clearly noticeable after just a few days of bed rest. A noticeable decrease in muscle strength becomes apparent, and patients then complain of a feeling of weakness and lethargy. They then need some time to regain their strength and return to their previous level of activity.

For this reason, patients are mobilized through physical therapy as soon as possible during a hospital stay. This helps preserve muscle mass to a large extent.

Mobilization and exercise prevent muscle atrophy in older adults. © gewitterkind / Fotolia

Muscle Wasting as a Distinct Disease

In contrast, when muscle wasting occurs as a neuromuscular disorder, both nerves and muscles are affected. The disease progresses relentlessly.

If the muscles themselves are diseased, this is referred to as myogenic muscle wasting, also known as myodystrophy or myopathy.

Neurogenic muscle wasting (spinal muscular atrophy) is diagnosed when the cause lies in the nerve cells.

Myogenic forms include

• Duchenne muscular dystrophy (DMD) and
• Becker muscular dystrophy (BMD).

These conditions occur almost exclusively in males.

In Duchenne muscular dystrophy, there is a defect in the dystrophin gene. Dystrophin is found in the cell membrane of muscle fibers and plays an essential role in muscle contraction. If this protein is missing, as in children with DMD, it leads to impairments in motor development.

Most children with DMD are never able to jump or run, and their gait is unsteady. Between the ages of 6 and 13, they typically lose the ability to walk independently. Due to heart muscle disease or respiratory failure, life expectancy is significantly reduced in this form of muscular dystrophy—patients usually die in early adulthood.

In contrast, Becker muscular dystrophy is caused by genetic mutations that result in a lack of dystrophin. This also leads to progressive muscle wasting and weakness. However, unlike the Duchenne form, life expectancy is usually not significantly reduced, or only to a minor extent. Life expectancy is, however, only slightly reduced or not reduced at all.

Well-known forms of neurogenic muscular atrophy include

• Werdnig-Hoffman disease (proximal spinal muscular atrophy type 1, SMA1) and
• Kugelberg-Welander disease (proximal spinal muscular atrophy type 3, SMA3)

The diseases were named after the scientists who researched them. These conditions are also genetically inherited but occur in both boys and girls.

SMA3 does not become apparent until after a child has learned to walk, manifesting as difficulty walking, etc. It progresses only slowly.

SMA1 appears within the first three months of life. Its symptoms are significantly more severe.

Children with SMA1 often die within the first two years of life; for children with SMA3, life expectancy is usually normal.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease. It does not appear until later in adulthood. The average age of onset is about 60 years.

In ALS, certain nerve cells (motor neurons) in the central or peripheral nervous system are damaged. This affects the muscles and, consequently, motor function. Depending on which motor neurons are affected, this can lead, among other things, to

• gait disturbances,
• twitching,
• paralysis,
• abnormal skin sensations,
• speech difficulties, and
• swallowing difficulties

may occur. As the disease progresses, additional symptoms such as muscle cramps and increasing weakness of the respiratory muscles often develop. The paralysis continues to advance. Consequently, the disease usually leads to death within a few years due to respiratory failure.

Only about 5 to 10 percent of ALS cases are familial (inherited); most arise spontaneously.

An overview of the most important and common causes of muscle wasting:

• advancing age or malnutrition
• Physical inactivity or (necessary) bed rest
• Genetic mutations, which lead to disturbances in muscle activity and the nervous system
• Autoimmune diseases
• Other diseases such as cancer or HIV infections

To detect muscle wasting early, it’s important to pay attention to small changes—the first signs are often overlooked or downplayed. These can include

• difficulty with everyday movements, such as climbing stairs and walking, or
• difficulty swallowing and speaking 

. A change in posture is also among the symptoms. The skeletal muscles are then no longer able to fully support the skeleton.

Children with congenital muscle weakness due to a genetic defect exhibit delayed physical development and often show similar symptoms, such as difficulty sitting down, standing up, or walking. Compared to children their age, their movement patterns are atypical, for example when

• sitting down,
• standing up, or
• walking.

Pediatricians therefore monitor the child’s developmental progress during regular checkups.

Physical therapy helps children with muscle wasting © Picture-Factory / Fotolia

An early diagnosis, even at birth, helps affected children. Appropriate therapies and orthopedic aids support the child’s physical development. 

People with muscle wasting experience significant weakness. They may also suffer from impaired organ function.

If muscle mass continues to decline,

• breathing becomes difficult,
• digestive function is impaired, and
• the heart is weakened.

If the disease is severe, muscle wasting can cause vital organ functions to fail. If breathing or the heart is affected, muscle wasting becomes a life-threatening condition.

Muscle disorders also occur in multiple sclerosis. However, muscle wasting is only loosely associated with multiple sclerosis. The difference lies primarily in the causes and symptoms.

Multiple sclerosis is a chronic inflammatory disease of the nerves. The myelin sheath—the electrically insulating outer layer of nerve fibers—is destroyed in episodes. Multiple sclerosis is therefore a neurological disease that results in disturbances of the muscle cells.

Multiple sclerosis is also known as the “disease with 1,000 faces” because its symptoms can be extremely diverse: muscle atrophy is one of them.

Muscle atrophy affects the entire body and its functions. Therefore, rehabilitation for muscle atrophy involves comprehensive therapeutic care covering all areas of life. A cure is only possible for muscle atrophy caused by inactivity. Otherwise, only the symptoms can be alleviated.

The goal of treatment is to improve quality of life and life expectancy. The aim is also to increase the patient’s independence. The following therapies and methods are used:

• Physical therapy with specialized exercises to build muscle and improve mobility
• Occupational therapy to train activities of daily living (ADL)
• Electrotherapy
• Massages and baths
• Ultrasound therapy
• Speech therapy (speech training) and swallowing therapy
• Supportive measures for respiratory and cardiac functions, such as respiratory support
• Early treatment of infections and complications
• Surgeries such as tendon shortening or spinal procedures
• Provision of assistive devices for walking and standing (for example, a walker) or a wheelchair
• Psychological counseling and social-medical support, including for family members
• Medication to treat the underlying condition (for example, steroids for Duchenne muscular dystrophy or riluzole for ALS)

Enzyme replacement therapy helps some patients, such as those with the glycogen storage disease Pompe disease. Enzyme replacement therapy involves administering specific proteins that are lacking in the bodies of some patients. Enzyme replacement therapy is a procedure that, in principle, is similar to diabetes treatment. It usually replaces the missing metabolic component for life.

Initial successes have also been achieved in the field of gene therapy in the laboratory. For example, in spinal muscular atrophy, defective genes can be replaced with functioning genes. The body can then produce the missing proteins again.

Medical professionals have high hopes that rare, hereditary neuromuscular disorders can be treated in the future using gene therapy methods.

Precise information about the causes is crucial for the prognosis: If a genetic disorder is the cause of the muscle wasting, the disease is considered irreversible and incurable.

The specific form of the muscular or neurological disorder determines the course of the disease and the life expectancy of those affected. There are cases with such a slow progression that life expectancy and quality of life are hardly affected. In cases with an unfavorable course, muscle function declines rapidly. Those affected usually die in young adulthood, sometimes even in early childhood.

However, a reduction in muscle mass can also be a result of inactivity. For this reason, mobilization and mobility are important supportive measures for seniors and bedridden individuals.

1. What is muscle wasting, and what forms does it take?
Muscle wasting refers to a pathological loss of muscle mass in which muscle tissue can gradually be replaced by fat and connective tissue. A distinction is made between myogenic forms (the muscles themselves are affected) and neurogenic forms (the nerve cells supplying the muscles are affected). In total, there are approximately 800 known forms of neuromuscular disorders.

2. What signs indicate muscle wasting?
Typical signs of muscle wasting include significant weakness, difficulty with everyday movements such as climbing stairs, standing up, or walking, and changes in posture. As the condition progresses, swallowing and speech difficulties, as well as impaired breathing and heart function, may also develop.

3. How is muscle wasting diagnosed?
The diagnosis of muscle wasting begins with a detailed medical history, during which symptoms, the course of the disease, and family history are documented. This is followed by a physical examination, which—depending on the suspected cause—may be supplemented by neurological tests, blood tests, electromyography (EMG), muscle biopsies, or genetic analyses.

4. Can muscle wasting be prevented?
Whether muscle wasting can be prevented depends on the cause: For older adults and bedridden individuals, regular exercise and early mobilization are the most important measures for slowing muscle loss.