1.4 Quality Assessment
Two independent reviewers (Z.H. and YN.L.) assessed the risk of bias in each study according to the risk of bias tool in the Cochrane Handbook for Systematic Reviews of Interventions (version 5.1.0); discrepancies were resolved by discussion with a third investigator (J.H.). Six domains assessed for each included study were as follows: (1) random sequence generation and allocation concealment; (2) blinding of participants and personnel; (3) blinding of outcome assessors; (4) incomplete outcome data; (5) selective reporting; (6) other bias.