Figure 2

Within studies ‘risk of bias assessment for RCT on five ROB 2 criteria and overall. The risk of bias evaluation in the categories: bias arising from the randomization process (R), bias due to deviations from intended interventions (D), bias due to missing outcome data (Mi), bias in measurement of the outcome (Me), bias in selection of the reported result (S); overall risk of bias (O). Red symbols: high risk of bias; yellow symbols: some concerns; green symbols: low risk of bias.