2.6 Data analysis
The Revman 5.3 software provided by Cochrane was used in this study. For continuous variable data, the random effects model or fixed effects model is used according to I2 of the combined total results. I2was used to evaluate heterogeneity. We considered that when I2 is greater than 50%, there is a large inter-group heterogeneity, so the random effect model was applied; when I2 is less than or equal to 50%, the inter-group heterogeneity is small, so the fixed effect model can be selected. For dichotomous results, a 95% confidence interval combined RR was used as a measure of efficacy. If the units of the variables were the same, WMD was used. Otherwise, we preferred to choice SMD.