Abstract
BACKGROUND: Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2. The role of skeletal muscle mass in modulating immune response is well documented. Whilst obesity is well established as a key factor in COVID-19 and outcome, no study has examined the influence of both sarcopenia (low muscle mass) and obesity, termed 'sarcopenic obesity' on the risk of severe COVID-19. METHODS: This study uses data from UK Biobank. Probable sarcopenia was defined as low handgrip strength. Sarcopenic obesity was mutually exclusively defined as the presence of obesity and low muscle mass [based on two established criteria: appendicular lean mass (ALM) adjusted for either (i) height or (ii) body mass index]. Severe COVID-19 was defined by a positive severe acute respiratory syndrome coronavirus 2 test result in a hospital setting and/or death with a primary cause reported as COVID-19. Fully adjusted logistic regression models were used to analyse the associations between sarcopenic status and severe COVID-19. This work was conducted under UK Biobank Application Number 52553. RESULTS: We analysed data from 490 301 UK Biobank participants (median age 70.0 years, 46% male); 2203 (0.4%) had severe COVID-19. Individuals with probable sarcopenia were 64% more likely to have had severe COVID-19 (odds ratio 1.638; P < 0.001). Obesity increased the likelihood of severe COVID-19 by 76% (P < 0.001). Using either ALM index or ALM/body mass index to define low muscle mass, those with sarcopenic obesity were 2.6 times more likely to have severe COVID-19 (odds ratio 2.619; P < 0.001). Sarcopenia alone did not increase the risk of COVID-19. CONCLUSIONS: Sarcopenic obesity may increase the risk of severe COVID-19, over that of obesity alone. The mechanisms for this are complex but could be a result of a reduction in respiratory functioning, immune response, and ability to respond to metabolic stress.