The demography
A total of 2,566 individuals were identified (771 in Severe group and 1,795 in Non-severe group) [14-27]. Specially, there were 12 studies reporting 409 males in 747 patients in Severe group (54.8%) and 843 males in 1,724 in Non-severe group (48.9%) [14-17, 19-25, 27]. With the pooled OR of 1.30 (95 % CI: 1.07 to 1.57), it was demonstrated that males were associated with significantly increased susceptibility of severe Covid-19. Consistently, of 14 studies reporting age of patients[15-27], it was revealed that older individuals were more susceptible to severe Covid-19 (WMD: 11.12, 95 % CI: 6.70 to 15.55). The outcome was explicitly expressed in Table 2.