Table 2. Risk of bias for included studies.

Study	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding of outcome assessment	Incomplete outcome assessment	Selective reporting	Other bias
Zhu 2018 (10)	Low	Low	Low	Unclear	Low	Low	High
Pan 2018 (33)	Low	Unclear	Unclear	Unclear	Low	Low	Low
Polkey 2018 (32)	Unclear	Unclear	Unclear	Unclear	Low	Low	Low
Ni 2017 (35)	Low	Unclear	Unclear	Unclear	Low	Low	Low
Ren 2017 (34)	High	High	Unclear	Unclear	Low	Low	Low
Ng 2014 (36)	Low	Low	Unclear	Low	Low	Low	Low
Zhang 2014 (38)	Low	Unclear	Unclear	Unclear	Low	Low	Low
Niu 2014 (37)	Low	Low	Low	Low	Low	Low	Low
Chan 2013 (39)	Low	Low	Low	Low	High	Low	Low
Leung 2013 (40)	Low	Low	Low	Low	Low	Low	Low
Chan 2013 (41)	Low	Low	Unclear	Unclear	High	Low	Low
Du 2013 (42)	Low	Unclear	Unclear	Unclear	Low	Low	Low
Du 2013 (43)	Unclear	Unclear	Unclear	Unclear	Low	Low	Low
Chan 2011 (44)	Low	Low	Unclear	Low	Low	Low	Low
Yeh 2010 (8)	Low	Unclear	Unclear	Low	Low	Low	Low
Zhou 2009 (45)	Unclear	Unclear	Low	Low	Low	Low	Low