Fig. 1.

Meta-regression analysis between the difference in age (DifAGE) and male proportion between the critical/mortal and non-critical groups of COVID-19 patients and the effect of comorbidities on COVID-19 critical illness among the studies.

Meta-regression was used to examine the impact of moderator variables (age and sex) on effect sizes using regression-based techniques. To determine the slope, we used meta-regression (methods of moments). Each circle represents a study according to the meta-analysis of Zheng et al.¹.