Risk of bias for the 11 included studies based on the ROBINS-I tool
| Study (author) | Year | Bias due to confounding | Bias in selection of participants into the study | Bias in classification of interventions | Bias due to deviations from intended interventions | Bias due to missing data | Bias in measurement of outcomes | Bias in selection of the reported result | Overall bias |
| Antonelli et al8 | 2006 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Tsai et al9 | 2011 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Peluso et al21 | 2011 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Wu et al22 | 2012 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Moderate risk | Moderate risk |
| Vassilatou et al15 | 2017 | Moderate risk | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk | Moderate risk |
| Kiguradze et al13 | 2017 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Moderate risk | Moderate risk |
| Haddad et al12 | 2017 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Fallahi et al11 | 2017 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Alidrisi et al10 | 2019 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Wang et al16 | 2019 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Low risk | Moderate risk |
| Valduga et al14 | 2021 | Moderate risk | Low risk | Low risk | Moderate risk | Low risk | Low risk | Moderate risk | Moderate risk |
ROBINS-I, Risk Of Bias In Non-randomised Studies-of Interventions.