Acknowledgements
We would express our heartfelt thanks to all the schoolchildren who participated in the study and their parents. We also appreciate the staff of Hunan Children’s Hospital for their support.
Consent for publication
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Author Contributions: XSH, JQ and YPC contributed to the conception and design of the work. JQ, MY and YM provisioned the study materials or patients. XSH collected and assembled the data. XSH performed the statistical analyses and interpretated. XSH drafted the manuscript. XSH and JQ revised the manuscript for important intellectual content. All authors contributed to the manuscript writing, and all authors read and approved the final version of manuscript.