Funding for this research was provided by:
Sanming Project of Medicine in Shenzhen (SZSM201511007)
Article History
Received: 21 June 2019
Accepted: 7 November 2019
First Online: 4 December 2019
Availability of data and materials
: The data sets generated and analyzed during the current study are not publicly available because these data are stored in a government system, but are available from the corresponding author on reasonable request.
: This study used secondary data, and information that can identify specific individuals (including children under 16) was not included. Ethics approval and consent to participate are not applicable.
: Not Applicable.
: The authors declare that they have no competing interests.