Could SARCOPENIA, the Loss of Muscle Mass, Be an Obstacle to Longevity?

As life expectancy increases worldwide, the older population is growing dramatically. However, aging also brings physical and functional losses. Among the most notable is a decline in skeletal muscle mass and strength, known as “sarcopenia.”

What Is Sarcopenia?

Sarcopenia is a condition characterized by loss of skeletal muscle mass, strength, and function during aging. It adversely affects many aspects of life, from mobility to independence and quality of life.

This article examines the causes and possible solutions to this serious condition from a scientific perspective, covering its definition, factors involved in its pathogenesis, diagnostic and assessment methods, and current and potential treatments.

Where Does the Name Sarcopenia Come From?

Sarcopenia was first described by Rosenberg in 1989, and its name derives from the Greek words “sarx” and “penia,” meaning “lack of flesh.” According to the European Working Group on Sarcopenia in Older People (EWGSOP), sarcopenia is a syndrome characterized by a progressive, generalized decline in skeletal muscle mass and strength. If not properly diagnosed and treated, sarcopenia can reduce quality of life, shorten lifespan, and impose a major economic burden on healthcare systems.

Symptoms of Sarcopenia

Symptoms of sarcopenia include:

1. Reduced Muscle Strength: Difficulty performing daily activities, such as opening a jar or carrying a bag.

2. Reduced Muscle Mass: Visible muscle loss, such as thinning of the arms or legs.

3. Balance and Coordination Problems: More frequent falls or tripping over carpets or objects.

4. Reduced Physical Performance: Slow walking speed, difficulty climbing stairs, or reduced endurance.

5. Low Energy and Easy Fatigability: Feeling more tired than usual during daily tasks.

6. Functional Loss: Inability to perform tasks that were previously easy.

7. Restricted Movement: Joint stiffness and loss of flexibility.

8. Social Isolation: Reduced social interaction because of impaired mobility.

These symptoms may progress over time and seriously affect quality of life. Early recognition and intervention are important in slowing sarcopenia.

Why and How Does Sarcopenia Develop?

Sarcopenia has a complex pathogenesis involving multiple mechanisms:

1. Neuromuscular Degeneration: Aging is accompanied by loss of motor neurons and atrophy of muscle fibers (type II, fast-twitch glycolytic fibers). This leads to reduced muscle mass and its replacement by adipose tissue.

2. Disordered Muscle Protein Metabolism: Aging disrupts the balance between protein synthesis and breakdown. In particular, reduced IGF-1/mTOR signaling and increased ubiquitin ligases such as atrogin-1 and MuRF-1 contribute to muscle loss.

3. Declining Hormone Levels and Sensitivity: Reduced testosterone, growth hormone (GH), and vitamin D levels are closely associated with loss of muscle mass and impaired function.

4. Chronic Inflammation and Oxidative Stress: The chronic inflammatory state associated with aging (“inflammaging”) disrupts muscle protein metabolism and activates catabolic pathways.

5. Behavioral Factors: Physical inactivity and inadequate nutrition play important roles in sarcopenia. Inadequate protein intake and a sedentary lifestyle can accelerate muscle loss.

How Is Sarcopenia Diagnosed?

The diagnosis of sarcopenia generally rests on two main parameters: low muscle mass and low muscle function. The following methods may be used:

1. Measuring Muscle Mass: Methods such as dual-energy X-ray absorptiometry (DEXA) and bioelectrical impedance analysis (BIA) are widely used to assess muscle mass.

2. Physical Performance Tests: Assessing physical performance with simple tests such as handgrip strength, walking speed, and the Chair Stand Test.

3. Biomarkers: Biomarkers such as IGF-1, myostatin, and interleukin-6 may be used for early diagnosis and monitoring of sarcopenia.

The Relationship Between Sarcopenia and Longevity

Independently of aging, sarcopenia increases the risk of physical disability, falls, fractures, metabolic disorders, and even premature death.

Numerical Evidence for the Relationship:

1. Loss of Muscle Mass:

   • After age 30, muscle mass decreases by 3-8% every 10 years, and this loss accelerates after age 60.
   • By age 80, muscle mass may have declined by 30-50%.

2. Loss of Muscle Strength:

   • Muscle strength declines faster than muscle mass. For example, leg muscle strength decreases by 10-15% every 10 years, rising to 25-40% after age 70.

3. Prevalence:

   • Sarcopenia may affect 10-27% of people over age 60 and reach up to 33% in those over age 70.
   • Sarcopenic obesity affects 18.1% of women and 42.9% of men over age 60.

4. Mortality and Survival:

   • Sarcopenia-related physical impairment and fall risk, together with fractures, lead to longer hospital stays and increased mortality.
   • Each 10% reduction in muscle strength may shorten lifespan by 7%.

5. Effects on Longevity:

   • Older adults with high muscle strength and physical performance have a 30-40% greater likelihood of living longer than those with low physical performance.

An Important Concept: SARCOPENIC OBESITY

Sarcopenic obesity is a condition in which age-related loss of skeletal muscle mass and strength (sarcopenia) occurs alongside excessive accumulation of body fat (obesity). This combination changes the muscle-to-fat ratio and adversely affects physical function, metabolic health, and overall quality of life.

Key Features:

1. Muscle Loss: Reduced skeletal muscle mass and strength due to sarcopenia.
2. Fat Gain: Excessive body fat accumulation due to obesity, usually in the abdomen.
3. Loss of Physical Function: Reduced mobility, slower walking speed, and difficulty with daily activities.
4. Metabolic Disorders: Insulin resistance and an increased risk of type 2 diabetes and cardiovascular disease.

Risk Factors:

• Aging: Age-related muscle loss combined with obesity.
• Low Physical Activity: A sedentary lifestyle accelerates muscle loss and contributes to fat accumulation.
• Inadequate Nutrition: Protein deficiency adversely affects muscle building.
• Hormonal Changes: Declining testosterone and growth hormone levels.

Clinical Effects:

• Risk of Falls and Fractures: Due to weakened muscles and the mechanical load imposed by increased adipose tissue.
• Inactivity and Social Isolation: Restricted physical activity, loneliness, and loss of independence.
• Increased Disease Burden: Metabolic syndrome, heart disease, and other inflammation-related diseases.

Treatment Approaches

1. Physical Activity: Progressive resistance exercise is considered the most effective treatment for improving muscle mass and function.

2. Nutrition: Increasing protein intake and supplementing deficient vitamins (such as vitamin D or B12) may help preserve muscle mass.

3. Hormonal Treatments: Testosterone replacement and selective androgen receptor modulators (SARMs) are potential treatments under investigation for increasing muscle mass.

4. Anti-inflammatory Treatments: Monoclonal antibodies targeting chronic inflammation and ACE inhibitors are promising treatments under investigation for sarcopenia.

Conclusion

Sarcopenia is a serious syndrome that reduces older people's quality of life and imposes a substantial burden on healthcare systems. Physical exercise and nutrition are the most effective approaches to managing this condition. However, developing new treatments that target its underlying pathophysiological mechanisms is crucial for prevention and management. Informing people about early diagnosis and preventive approaches is essential for healthier aging.