Sarcopenia is a type of muscle loss (muscle atrophy) that occurs with aging and/or immobility. It is characterized by the degenerative loss of skeletal muscle mass, quality, and strength. The rate of muscle loss is dependent on exercise level, comorbidities, nutrition, and other factors; it is related to changes in muscle synthesis.
It is distinct from cachexia, in which muscle is degraded through cytokine-mediated degradation, although both conditions may co-exist. It is a component of frailty syndrome that can lead to reduced quality of life and disability.