Risk of bias in individual studies
Study quality was assessed independently by two reviewers based on the seven domains defined by the Cochrane Collaboration’s tool for assessing risk of bias.14 The tool includes the following 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. We rated each domain as low risk, unclear risk, or high risk of bias. We assigned individual trials as high risk of bias if one or more domain(s) was deemed high risk of bias; otherwise, we assigned individual trials as low risk of bias.