“…The basic characteristics of the 15 studies are summarized in Table 1. All of them were retrospective observational studies [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. More than half of these studies (n ¼ 8) were conducted in Asian countries, including four in Japan [17,19,27,29], two in China [20,31], one in Korea [25], and one in Turkey [30].…”