Baseline physical activity and the risk of severe illness and mortality from COVID-19: A dose-response meta-analysis

To provide a scientific basis for improved exercise-based immunity, a meta-analysis was used to explore the dose-response relationship between physical activity (PA) and the risk of severe illness and mortality related to COVID-19 (coronavirus disease 2019). To this end, we searched PubMed, Web of Science databases from January 2020 through April 2022. 14 observational studies met the criteria for inclusion in the meta-analysis, including 2840 cases of severe illness and death from COVID-19. Categorical dose-relationship analysis showed that the risks of severe illness and mortality from COVID-19 were, respectively, 46% (risk ratio (RR): 0.54; confidence intervals (CIs): 0.41-0.68) and 59% (RR = 0.41; 95%CI: 0.23-0.58) lower for the highest dose of PA compared with the lowest dose of PA. The results of the continuous dose-response analysis show an inverse nonlinear relationship (P_{non-linearity} < 0.05) between PA and both the risk of severe illness and mortality from COVID-19. For PA below 10 MET-h/week (MET-h/week: metabolic equivalent of task-hours/week), an increase of 4 MET-h/week (1 h of moderate-intensity or 0.5 h of high-intensity PA) was associated with 8% and 11% reductions in the risk of severe illness and mortality from COVID-19. PA above 10 MET-h/week lowered the risk of severe illness and mortality from COVID-19 by 7% and 9%, respectively, for each 4 MET-h/week increase. Doses of WHO-recommended PA levels (10 MET-h/week) may be required for more substantial reductions in the risk of severe illness and mortality from COVID-19.