Received: 9 April 2021
Accepted: 24 September 2021
First Online: 19 October 2021
: The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The present study was approved by the Medical Ethics Committee of Bengbu Medical College [2015 No. 003] and informed consent was taken from all the participants (or their parents) before the survey.
: Not applicable.
: The authors declare that they have no competing interests.