2.4. Data analysis
One reviewer extracted descriptive characteristics and effect estimates for each outcome of interest from the included studies and recorded them on a data extraction form, which the remaining authors verified for accuracy. Risk of bias for each included study was assessed in selection, performance and attrition bias (5). We described the review findings narratively for each predefined outcome, and when feasible, pooled the effect estimates in a random effects meta-analysis according to the DerSimonian and Laird method (5). RevMan (Review Manager (RevMan) [Computer program]. Version 5.4. The Cochrane Collaboration, 2020) was used to conduct these analyses.
To obtain an explicit judgement on the confidence in the review findings, we classified the quality of evidence for each outcome as high, moderate, low, or very low according to the GRADE working group guidance (7). We also integrated judgements on the quality of the evidence into a summary of findings table (8), which included the effect estimates for the outcomes of interest.