Funding for this research was provided by:
China National Funds for Distinguished Young Scientists (81402699)
the National Natural Science Foundation of China (81573512)
Text and Data Mining valid from 2019-09-12
Received: 18 April 2019
Accepted: 4 September 2019
First Online: 12 September 2019
Ethics approval and consent to participate
: Approval for the study was granted by the Ethics Committee of Anhui Medical University (Mar. 1, 2014; approval number 20140087). Any information that could distinguish individual participants was not collected during the data collection process. We had signed informed consent with each participating school, which the students were allowed to participate in the study upon receiving completed written consent form from their parents.
: Not applicable.
: The authors declare that they have no competing interests.