Muscle atrophy

Major loss of muscle protein as described as atrophy or wasting, is commonly seen in old age and referred to as sarcopenia, in cases of muscle disease or denervation, and in systemic inflammatory catabolic states.

Loss of skeletal muscle mass and function has mental, social, and physical health consequences impairing the quality-of-life and increases the risk of additional complications and mortality.

Muscle mass begins to decline about age 40 years.

Mean muscle loss approximately 8% per decade until the age of 70.

After the age of 70 years muscle mass decline accelerates to 25-40% per decade.

Involves skeletal muscle loss and not visceral protein loss.

Lower muscular strength is related to mental health issues such as depression.

In starvation muscle mass is lost in proportion to visceral protein loss.

Muscle protein synthesis decreases with aging partly due to endocrine changes with reduction in sex hormones and growth factors.

Muscle protein breakdown increases with age, mainly because of age-related low-grade systemic inflammation, physical inactivity and malnutrition.

Loss of lean body mass is directly linked to the morbidity and mortality of the conditions leading to muscle atrophy.

Referred to as sarcopenia in the geriatric age group and associated with low muscle mass combined with low muscle strength or impaired physical performance.

Loss of muscle mass associated with poor outcomes in chronic diseases, such as cirrhosis and cardiovascular disease.

Frequently associated with HIV, rheumatoid arthritis and diabetes.

When total body weight loss reaches 30% death occurs as respiratory failure from hypostatic pneumonia occurs through erosion of the diaphragm.

Loss of skeletal muscle is associated with a poor prognosis in all the conditions associated with muscle atrophy.

Survivors of critical illness experience significant skeletal muscle weakness and physical disabilities which can persist for up to five years.

Muscle wasting/atrophy contributes substantially to weakness that is acquired during an ICU stay.

The pathophysiology of muscle atrophy is probably related to increased breakdown of muscle relative to synthesis.

Protein synthesis is refractory in the early stages of critical illness and increasing protein delivery is associated with increased muscle wasting.

During critical illness decreased protein synthesis occurs due to immobility and endotoxin exposure.

Surgical patients with low muscle mass associated with postoperative complications.

Critical illness is associated with an early myelopathic process.

Inflammation reduces protein synthesis and increases breakdown.

Low-grade systemic inflammation (inflammaging)that occurs with aging is characterized by elevated proinflamatory cytokines and is caused by age-related cell damage and mitochondrial dysfunction, leading to increased oxidative stress.

Lung derived inflammatory mediators are associated with muscle wasting chronic lung disease.

Associated with low hemoglobin concentrations, and metabolic acidemia in acute illness.

Patients with low muscle mass have a greater likelihood of experiencing more severe toxicities from anti-tumor agents.

Many chemotherapy agents are distributed to the fat-free body compartments, and with the decline of muscle mass there is a relatively increased drug concentrations.

Men experience faster deterioration of muscle mass and muscle strength compared with women, at older age.

Muscle strength in elderly has a higher association with morality than muscle mass.

Muscle strength deteriorates more rapidly than muscle mass.

Promoting muscular strength among elderly people is important, and it is recommended that older people should engage in muscle strengthening activities involving major muscle groups two or more days a week.

Resistance training results in significant improvement in strength, and significantly reduces depressive symptoms among adults so that a physical activity routine including both aerobic and muscle strengthening activities is optimal for the prevention of depression.