Table 2 Quality assessment of the enrolled studies
Authors | Selection | Comparability | Exposure |
|---|---|---|---|
Katsuura2001 et al [35] | ★★★★ | ★★ | ★★★ |
Kim2015 et al [36] | ★★★★ | ★★ | ★★★ |
Lee2015 et al [37] | ★★★★ | ★★ | ★★★ |
Li2014 et al [38] | ★★★★ | ★★ | ★★ |
Song2014 et al [39] | ★★★ | ★★ | ★★★ |
Song2018 et al [40] | ★★★★ | ★★ | ★★ |
Yang2017 et al [41] | ★★★ | ★★ | ★★★ |