Sarcopenic obesity and the risk of hospitalisation or death from COVID-19: findings from UK Biobank

Wilkinson, T.; Yates, T.; Baker, L. A.; Zaccardi, F.; Smith, A. C.

Background Coronavirus disease-2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS;CoV-2 virus). 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 infection and outcome, no study has examined the influence of both sarcopenia (low muscle mass) and obesity, termed sarcopenic obesity on COVID-19 risk. 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: 1) height and 2) body mass index (BMI)). Severe COVID-19 was defined by a positive test result in a hospital setting 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. 2203 (0.4%) had severe COVID-19 infection. Individuals with probable sarcopenia were 64% more likely to have had severe COVID-19 infection (odds ratio (OR) 1.638; P<.001). Obesity increased the likelihood of severe COVID-19 infection by 76% (P<.001). Using either ALM index and ALM/BMI index to define low muscle mass, those with sarcopenic obesity were 2.6 times more likely to have severe COVID-19 (OR: 2.619; P<.001). Sarcopenia alone did not increase the risk of COVID-19. Conclusions Sarcopenic obesity may increase the risk of severe COVID-19 infection, 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.