How is sarcopenia distinguished from other conditions?

There are three main conditions that overlap with sarcopenia: frailty, malnutrition, and cachexia. Frailty is a state of increased vulnerability due to cumulative decline in multiple physiological systems^[1] and involves adverse effects to physical, cognitive, and social dimensions.^[2] Sarcopenia contributes to the physical aspect of frailty, but it differs from frailty because it only affects the musculoskeletal system, whereas frailty is a much broader condition.

Both malnutrition and sarcopenia are characterized by low muscle mass, but sarcopenia also includes impaired muscle function. Additionally, reduced fat mass is typically present in malnutrition, but not sarcopenia.^[3]

Cachexia is described as severe weight loss and muscle wasting associated with conditions such as cancer, HIV/AIDS, or end-stage organ failure. Cachexia and sarcopenia may coexist, but the presence of the aforementioned conditions suggests that cachexia is more likely.^[4] Unlike sarcopenia, cachexia is characterized by systemic inflammation, as indicated by low serum albumin and elevated C-reactive protein levels.^[5] The diagnosis of cachexia also typically requires unintentional weight loss of at least 5% of body weight in the past six months.^[5]