Funding for this research was provided by:
The fiftieth Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry
The Science and Technology Basic and Advanced Research Projects in Chongqing (cstc2014jcyjA10069)
Received: 9 April 2018
Accepted: 16 August 2019
First Online: 23 August 2019
Ethics approval and consent to participate
: The project proposal was approved by the Institutional Review Board of Preventive Medicine College, Army Medical University (Third Military Medical University), Chongqing, China. Written informed consent was obtained from all the participants once they agreed to take part in the study.
: Not applicable
: The authors declare that they have no competing interests.