*2.2. Risk of Bias Assessment*

The risk of publication bias of each included study was assessed using the "Cochrane Guide for Review Authors on Assessing Study Quality", which is based on "Cochrane Collaboration's tool for assessing risk of bias" [15]. This tool classifies the risk of bias in randomized controlled trials (RCTs) included in reviews as either "High risk", "Unclear" or "Low risk" in accordance with 7 domains—random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting and other sources of bias [16]. This classification was independently assigned by 2 authors and discrepancies in assessment were resolved through discussions between the authors or by consultation with a third researcher. The results of the risk of bias assessment were presented in a risk of bias summary and a risk of bias graph, which were sketched using the software Review Manager 5.3 (Version 5.3.5) (http://community.cochrane.org/).
