Table 2.

Risk of bias of the included studies

Study	A	B	C	D	E	F	G	H	I	J	Toal
Chehelcheraghi et al., 2020 [48]	+	+	–	?	?	?	+	+	+	?	5
Chehelcheraghi et al., 2019 [8]	+	+	–	?	?	?	?	+	+	?	4
Chehelcheraghi et al., 2016 [47]	+	+	–	?	?	?	?	+	+	?	4
Chehelcheraghi et al., 2015 [46]	+	+	–	?	?	?	?	+	+	?	4
Ding et al., 2020 [45]	?	+	–	?	?	?	?	+	+	?	3
Feng et al., 2020 [44]	+	+	–	?	+	+	+	+	+	?	7
Gao et al., 2011 [43]	+	+	–	?	?	?	+	+	+	?	5
Han et al., 2015 [42]	+	+	–	?	?	+	+	+	+	?	6
Leng et al., 2017 [41]	+	+	–	?	?	+	?	+	+	?	5
Leng et al., 2012 [40]	+	+	–	?	?	+	+	+	+	?	6
Moon, 2018 [39]	+	+	–	?	?	+	+	+	+	?	6
Pak et al., 2020 [28]	?	+	–	?	?	?	?	+	+	?	3
Park et al., 2017 [38]	+	+	–	?	?	?	?	+	+	?	4
Pu et al., 2017 [19]	?	+	–	?	?	?	?	+	+	?	3
Reichenberger et al., 2012 [37]	+	+	–	?	+	?	+	+	+	?	5
Suartz et al., 2014 [36]	+	+	–	?	?	?	?	+	+	?	4
Tang et al., 2016 [35]	?	+	–	?	?	?	?	+	+	?	3
Wang et al., 2011 [34]	+	+	–	?	?	+	?	+	+	?	5
Yang et al., 2010 [33]	+	+	–	?	?	+	?	+	+	?	5
Zhou et al., 2019 [18]	+	+	–	?	?	?	+	+	+	?	5

Studies fulfilling the criteria of A sequence generation, B baseline characteristics, C allocation concealment, D random housing, E blinding of investigators, F random outcome assessment, G blinding of outcome assessor, H complete outcome data, I selective outcome reporting, and J other sources of bias