Quality assessment
The risk of bias of each study was conducted using the Risk of Bias
table in Review Manager 5.4.1 to critically judge the information within
each article and to evaluate whether each study involved in
meta-analysis meets the internal validity criteria. Standard criteria
including sequence generation (selection bias), allocation concealment
(selection bias), blinding of participants and personnel (performance
bias), blinding of outcome assessment (detection bias), incomplete
outcome data (attrition bias), selective reporting (reporting bias) were
used to assess the quality of each study. The risk of bias was
classified into low, unclear, or high with explanations given for each
criterion. Publication bias was also accessed using funnel plots.