Table 2 Risk of bias for non-randomized studies
| Â | Selection | Comparability | Exposure | Assessment |
|---|---|---|---|---|
Yang et al. [26] | Low (4 pts) | Low (2 pts) | High (2 pts) | Good |
Bailey et al. [25] | Low (4 pts) | High (1 pt) | Low (3 pts) | Good |
Everhart et al. [33] | Low (3 pts) | High (1 pt) | Low (3 pts) | Fair |
Dai et al. [19] | Low (4 pts) | High (1 pt) | Low (3 pts) | Good |
Kemmochi et al. [32] | Low (4 pts) | Low (2 pts) | High (2 pts) | Good |
Pujol et al. [30] | Low (4 pts) | High (1 pt) | Low (3 pts) | Good |
Griffin et al. [20] | Low (3 pts) | High (1 pt) | High (2 pts) | Fair |