Risk of bias and individual quality of the studies

The risk of bias and individual quality of the studies selected was assessed by the Joanna Briggs Institute Critical Appraisal Tools for use in JBI Systematic Reviews Checklist for Randomized Controlled Trials [31]. Two authors assessed each domain independently and systematically regarding the potential risk of bias, as recommended by the PRISMA [29]. The reviewers solved any disagreements through discussions, and when both reviewers disagreed, they consulted a third reviewer for a final decision.

The following criteria were used for the assessment: Q.1) Was true randomization used for assignment of participants to treatment groups?; Q.2) Was allocation to treatment groups concealed?; Q.3) Were treatment groups similar at the baseline?; Q.4) Were participants blind to treatment assignment?; Q.5) Were those delivering treatment blind to treatment assignment?; Q.6) Were outcomes assessors blind to treatment assignment?; Q.7) Were treatment groups treated identically other than the intervention of interest?; Q.8) Was follow up complete and if not, were differences between groups in terms of their follow up adequately described and analyzed?; Q.9) Were participants analyzed in the groups to which they were randomized?; Q.10) Were outcomes measured in the same way for treatment groups?; Q.11) Were outcomes measured in a reliable way?; Q.12) Was appropriate statistical analysis used?; Q.13) Was the trial design appropriate, and any deviations from the standard RCT design (individual randomization, parallel groups) accounted for in the conduct and analysis of the trial?.

The risk of bias for a study was ranked as “high” when up to 49% of the answers corresponded to "yes", “moderate” when 50% to 69% of the answers corresponded to "yes", and “low” when more than 70% of the answers corresponded to "yes".