Data analyses
Two authors separately collected the required, relevant data with any discrepancies between them being resolved by group consultation. The two authors used the Cochrane collaborative bias risk tool to assess the risk of bias independently in five aspects and used the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) to estimate the quality of evidence for each outcome.[15] The results of each RCT were assigned as dichotomous data, analysed by the Mantel Haenszel method, and presented as relative risk (RR). The summary RR and 95% confidence interval (CI) of the survey results were calculated using a random effect model.[16] P ≤ 0.5 was considered to be statistically significant, and heterogeneity was assessed through I‐square (I2) and Q statistics; I2> 50% is considered substantial[17,18]. Using funnel plots[19], Egger and Begg tests were conducted to evaluate the publication bias of studies with reported results ≥ 10.[20]