Acute Sarcopenia Secondary to Hospitalisation - An Emerging Condition Affecting Older Adults

Abstract

There has been increasing interest and research into sarcopenia in community-dwelling older adults since the European Working Group on Sarcopenia in Older People (EWGSOP) agreed a consensus definition in 2010. Sarcopenia has been defined as loss of muscle mass with loss of muscle function (strength or physical performance), with measurements two Standard Deviations (SDs) below the mean of a young reference population. This definition does not necessitate longitudinal measurements, or the absence of acute illness and diagnosis can be made from single measurements. We hypothesise that hospitalisation, due to a combination of acute inflammatory burden and muscle disuse, leads to an acute decline in muscle mass and function and may lead to some individuals meeting criteria for sarcopenia, acutely, based on the EWGSOP definition. This may be partially recoverable or may lead to increased risk of developing sarcopenia long-term. We have denoted the term "acute sarcopenia" to refer to acute loss of muscle mass and function associated with hospitalisation. This review discusses some of the current available research in this context and also identifies some of the knowledge gaps and potential areas for future research.

Keywords: acute illness; disuse muscle atrophy; hospitalisation; muscle wasting disorders; sarcopenia.

Figure 1.. Acute sarcopenia as part of a spectrum of acute muscle wasting disorders

This schematic demonstrates the relationship between underlying predisposing factors and precipitating factors resulting in acute sarcopenia or acute muscle wasting. Physiologically fit adults who are immunocompetent may experience significant muscle wasting in the context of a critical illness necessitating admission to the intensive care unit. Conversely, frail older adults with immunosenescence may develop acute sarcopenia following a seemingly minor physiological stressor event such as a mild infection or short periods of bed rest.

Figure 2.. Proposed disease trajectories associated with sarcopenia

This diagram demonstrates proposed trajectories associated with the development of sarcopenia over time. The green line demonstrates expected changes of muscle mass and function associated with healthy ageing; there may be some inevitable loss of muscle mass and function but not to such an extent as to cause detriment. The blue line demonstrates the development of chronic sarcopenia over time. The red line demonstrates our proposed model of how episodes of acute sarcopenia can potentially lead to the development of chronic sarcopenia over time.

Figure 3.. Potential effectors of "acute sarcopenia" secondary to hospitalisation

There are likely to be multiple potential factors that can increase an individual’s likelihood of developing acute sarcopenia. Some of these are person-specific factors that lead to an increased predisposition to developing this condition; others relate to the stressor event itself. Many of these effectors are potentially amenable to prevention or intervention.