Funding for this research was provided by:
Department of Education of Guangdong Province (2017KQNCX068)
Received: 2 January 2020
Accepted: 21 July 2020
First Online: 31 July 2020
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Shantou University Medical College, and written, informed consent was obtained from all study participants.
: Not applicable.
: The authors have no conflicts of interest to declare.