Acknowledgments
Ming-Liang Zhang, Fang-Zhou Liu and Xiao-Long Chen conducted the
literature search and study selection, performed data extraction and
evaluated study quality. Wei-Xia Li, Xiao-Yan Wang and Hui Zhang
verified quality assessments. Pan-Pan Chen and Wen-Hui Jia performed the
quantitative meta-analyses and drafted the manuscript with contributions
from the other authors. Lu Niu and Yan Wang helped in the interpretation
of results. Jin-Fa Tang was responsible for the project and participated
in its implementation. All authors read and approved the final
manuscript.