Contribution to authorship
YH Shi and QM Wang conceived and
designed this study. QM Wang contributed to the statistical analyses,
interpretation of data and drafting of the manuscript. YJ Zheng and P Li
performed statistical analyses and participated in discussions. GQ Zhang
acquired the data. SS Gao and Z Wang analysed and interpreted the data.
YH Shi and QM Wang participated in the discussion and critically revised
the manuscript. All authors read and approved the final manuscript.