Risk of bias assessment
| Study | Potential risk of bias item | Risk of bias | |||||
| 1 | 2 | 3 | 4 | 5 | 6 | ||
| Bennell et al 16 | + | + | − | + | − | + | High |
| Cameron et al 30 | − | + | + | − | − | + | High |
| Croisier et al 19 | + | + | + | + | − | + | Low |
| Dauty et al 20 | + | + | − | + | − | − | High |
| Fousekis et al 18 | + | + | − | − | − | + | High |
| Henderson et al 15 | + | + | + | + | + | + | Low |
| Orchard et al 17 | + | − | + | + | − | + | High |
| Sugiura et al 33 | + | + | − | + | + | + | Low |
| van Dyk et al 14 | + | + | + | + | + | + | Low |
| Yamada and Mastumoto31 | − | + | − | − | − | − | High |
| Yeung et al 32 | + | + | + | + | − | + | Low |
| Zvijac et al 8 | + | + | + | + | − | + | Low |
1—study participation; 2—study attrition; 3—prognostic factor measurement; 4—outcome measurement; 5—study confounding variables; 6—statistical analysis and reporting.