Role of sarcopenia risk in predicting COVID-19 severity and length of hospital stay in older adults: a prospective cohort study

Coronavirus disease 2019 (COVID-19) has been a public health emergency since March 2020⁽¹⁾. This severe acute respiratory syndrome coronavirus 2 has infected over 480 million individuals and caused more than 6 million deaths worldwide⁽²⁾. The common symptoms of COVID-19 are fever, fatigue, headache, diarrhoea, anorexia and loss of taste and smell, as well as respiratory symptoms such as cough and shortness of breath. Moreover, interstitial pneumonia may result in acute respiratory distress syndrome with subsequent sepsis-induced coagulopathy and multiple organ dysfunction^(3,4). Adherence to safety measures and strengthening the immune system are important approaches for protecting individuals against COVID-19 until approved pharmacological therapies and vaccines become globally available^(3,5).

The overall prevalence and number of severe cases of COVID-19 are higher among older individuals⁽⁶⁾. Factors such as sarcopenia, chronic diseases and nutritional inadequacy, which are more prevalent in older adults, can adversely affect the immune system and physiological function^(6–8).

Particularly, sarcopenia is a progressive, generalised skeletal muscle disorder defined by the loss of muscle mass, physical performance and strength^(9,10). Risk factors for this disorder include ageing, nutritional deficiency, chronic diseases, physical inactivity, anxiety and very low 25-hydroxyvitamin D levels⁽¹¹⁾. The prevalence of sarcopenia in the elderly ranges from 9·9 to 40·4 %, according to a systematic review⁽¹²⁾. This prevalence’s range depend on factors such as the reference used for its definition, age, gender and ethnicity^(11,13). Specifically, different definitions of sarcopenia do not necessarily measure the same underlying variables; thus, even within the same population, sarcopenia estimation can vary depending on the definition⁽¹⁴⁾. In addition, sarcopenia is more prevalent among non-Asian individuals⁽¹⁵⁾, men older than 80 years and women younger than 70 years⁽¹⁶⁾.

Nutritional status, sarcopenia and the immune system are strongly related to each other. Nutritional deficiency exacerbates sarcopenia and as a result will weaken the immune system⁽¹⁷⁾. In COVID-19 patients, sarcopenia can cause deterioration of respiratory system function by weakening the muscles involved in respiration. Moreover, it can increase the risk of aspiration because of its negative impact on the muscles involved in swallowing^(11,18). On the other hand, a combination of obesity and sarcopenia can result...