“…Twenty-one studies , which included 13,790 hospitalized patients with COVID-19 with a mean age ranging from 50 to 70.3 years, and with sample sizes ranging from 54 to 4,526, were published from 2020 to 2021 [eight of them published in 2021 (11,15,16,19,(24)(25)(26)31), others in 2020 (12-14, 17, 18, 20-23, 27-30)]. Nine reports were from Asia [eight from China (13,16,18,21,22,28,29,31), one from Iran (19)], seven from USA (11,12,14,15,17,25,30), and five from Europe [three from Italy (20,24,27), one from Netherland (23), one from Germany (26)]. Besides, 15 of them were retrospective studies (11, 13, 15-19, 21-23, 27-31), 5 were prospective studies (12,14,20,25,26), and 1 was cross-section study (24).…”