Table 2 The risk of bias of the included studies
Author | Random sequence generation | Allocation concealment | Blinding of participants and personnel | Blinding of outcome assessment | Incomplete outcome data | Selective reporting | Other bias |
|---|---|---|---|---|---|---|---|
Ahn et al. [18] 2013 | Low risk | Unclear | Unclear | Unclear | High risk | Low risk | Low risk |
Ritsuno et al. [21] 2014 | Unclear | Low risk | Unclear | Unclear | Low risk | Low risk | Low risk |
Koike et al. [19] 2015 | Low risk | Low risk | Unclear | Unclear | Low risk | Low risk | High risk |
Mori et al. [20] 2017 | Unclear | Low risk | Unclear | Unclear | Low risk | Low risk | Unclear |
Yamasaki et al. [22] 2018 | Low risk | Unclear | High risk | Unclear | Low risk | Low risk | Unclear |
Yoshida et al. [23] 2018 | Low risk | High risk | High risk | Unclear | Low risk | Low risk | Unclear |
Ban et al. [24] 2018 | Low risk | Unclear | Unclear | Unclear | Low risk | Low risk | High risk |