Funding for this research was provided by:
Wuhan University Population and Health Young Academic Team (Whu2016026)
Article History
Received: 23 July 2019
Accepted: 14 January 2020
First Online: 22 January 2020
Compliance with Ethical Standards
:
: The authors declare that they have no conflict of interest.
: Ethical Approval was not required because the data we used were public and had anonymous characteristics.