Table 2. Bias risk evaluation of studies included in the meta-analysis.

Studies	Random sequence generation	Allocation concealment	Blinding	Incomplete outcome data	Selective reporting	Other bias
Guo M 2009 [51]	Low risk	Unclear risk	Unclear risk	Low risk	Low risk	Unclear risk
Ng 2010 [48]	Low risk	Low risk	Low risk	Low risk	Low risk	Unclear risk
Yano 2012[50]	Low risk	Unclear risk	Unclear risk	Low risk	Low risk	Low risk
Wang YP 2012 [53]	Unclear risk	Unclear risk	Unclear risk	Unclear risk	Low risk	Unclear risk
Sun RR 2012 [52]	Unclear risk	Unclear risk	Unclear risk	Unclear risk	Low risk	Unclear risk
Ng 2012 [49]	Low risk	Low risk	Low risk	Low risk	Low risk	Unclear risk
Hu L 2012 [54]	Unclear risk	Unclear risk	Unclear risk	Unclear risk	Low risk	Unclear risk
Wang J 2012 [56]	Low risk	Unclear risk	Unclear risk	Low risk	Low risk	Unclear risk
Lu BJ 2013 [55]	Unclear risk	Unclear risk	Unclear risk	Unclear risk	Low risk	Unclear risk