Author Contributions
Su-Mei Xu, Qiu-Ying Sheng, Xu-Feng Zhong, Xiao-Min Li, Wang-Li Liu,
Xiao-Lei Hu and were involved in study design, data analysis and
interpretation; Ping-sheng Xu was involved in data analysis and
interpretation. Su-mei Xu drafted the manuscript.
All authors critically reviewed the
manuscript and approved the final draft.