Statistical Analysis
This meta-analysis was performed using the Review Manager software (RevMan V.5.3; Cochrane Collaboration, Oxford, UK). Cochrane Q statistics and Chi-square test was used to determine whether heterogeneity existed among studies. If the heterogeneity (p<0.1, I² >50%), the random effects model was used for meta-analysis. If there was no significant heterogeneity between studies (P≥0.1, P≤50%), The fixed effects model is adopted. For dichotomous variables, relative risk (RR) and 95% confidence interval (CI) were used. For continuous variables, when the measuring tools and units used in each document for an index are completely the same. The weighted mean difference (WMD) and 95% CI were used to represent. When they are not completely the same, standard mean difference (SMD) and 95% CI are used. A P<0.05 was considered to be statistically significant. For outcome where quantitative data cannot be synthesized, narrative analysis is performed. Since the number of studies that included the results of the meta-analysis was not more than 10, we did not use funnel plot for publication bias.