The statistical package (RevMan 4.3.2) was used for data analyses, which was provided by The Cochrane Collaboration. Dichotomous data were presented as risk ratio (RR) and continuous outcomes as mean difference (MD), both with 95% confidence interval (CI). Meta-analysis was performed if the intervention, control, and outcome were the same or similar. The statistical heterogeneity was presented as significant when I square (I 2 ) is over 50% or P < 0.1. Random effect model was used for the meta-analysis if there was significant heterogeneity (I 2 > 50%) and fixed effect model was used when the heterogeneity was not significant (I 2 < 50%) [7] .