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The term secondary sarcopenia refers to loss of muscle mass as a result of disuse (for example, stroke or prolonged bedrest), and/or the presence of chronic diseases with varying degrees of upregulation of inflammatory cytokines, but distinct from the condition of cachexia. For example, the prevalence of sarcopenia in patients with heart failure (HF) is 20% higher compared with healthy subjects of the same age, and not confined only to the older age groups. There is increased catabolic stress in the skeletal muscle of HF patients, presenting clinical as reduced exercise tolerance, ventilator inefficiency, as well as inefficient chronotropic response. Malnutrition as a result of anorexia caused by inflammatory cytokines also aggravates muscle loss. Both malnutrition and sarcopenia are commonly observed among patients undergoing rehabilitation, the prevalence of both conditions ranging from 40 to 67% [32].

The relationship between secondary sarcopenia and cachexia is not distinct and may be viewed as a transition between the two states. While muscle loss occurs in cachexia, the underlying disease state plays a prominent role with its associated anorexia, weight loss, fatigue, and reduced physical activity. Anorexia, inflammation, insulin resistance, and increased muscle breakdown are more marked in cachexia, while inflammatory cytokines such as interleukin‐6 and tumor necrosis factor are highly elevated compared with sarcopenia [33].