sarcopenia

Sarcopenia is a syndrome characterized by progressive loss of skeletal muscle mass and strength, often associated with aging, which leads to functional impairment and increased risk of disability, falls, and dependence. The condition may occur with or without concurrent loss of muscle mass, sometimes described as dynapenia when strength declines more than muscle size.

Risk factors include advancing age, physical inactivity, poor protein intake, and chronic diseases such as diabetes, cardiovascular disease, and inflammatory conditions. Obesity can coexist with sarcopenia, a combination sometimes referred to as sarcopenic obesity, which compounds functional decline.

Pathophysiology involves diminished muscle protein synthesis, anabolic resistance to protein intake, loss of motor neurons, and changes in muscle fiber composition, particularly type II fibers. Chronic low-grade inflammation, hormonal changes (reduced growth and sex steroid signaling), mitochondrial dysfunction, and oxidative stress contribute to muscle deterioration.

Diagnosis relies on objective measurements of muscle mass and function. Low muscle mass can be assessed by dual-energy X-ray absorptiometry (DXA) or bioelectrical impedance analysis (BIA). Muscle function is evaluated with strength tests such as handgrip strength and performance tests such as gait speed or the short physical performance battery. Screening tools like SARC-F may indicate risk.

Management emphasizes physical activity, particularly resistance training to improve strength and mass, and adequate protein intake (often around 1.0–1.2 g/kg/day, higher in some individuals). Vitamin D sufficiency, addressing comorbidities, and strategies to prevent falls are important. Pharmacologic therapies are investigational and not widely approved.

Prognosis varies with severity and comorbidity, but sarcopenia is linked to higher rates of hospitalization, loss of independence, and mortality. Prevention focuses on lifelong physical activity and balanced nutrition, especially through older adulthood.