Data Synthesis
For continuous data, we used the inverse-variance method and the data were pooled as mean difference (MD) using Review Manager Software (version 5.3) for windows. For dichotomous data, we used the Mantel-Hanszel method and the data were pooled as relative risk (RR) using OpenMeta [Analyst] software for windows. We assessed the heterogeneity by the Chi-square test and its extent was determined byI -square, such that values of p < 0.1 or I2>50% were significant indicators of heterogeneity. We used the random-effects model to analyze heterogeneous data and fixed-effects model for the analysis of homogeneous data and performed a sensitivity analysis to solve the heterogeneity whenever detected.