Funding for this research was provided by:
National Natural Science Foundation of China (71673187, 71273174)
Shanghai Key Discipline Construction Project in Public Health (15GWZK1002)
Received: 12 May 2019
Accepted: 17 October 2019
First Online: 11 December 2019
Ethics approval and consent to participate
: The ethics committee of the School of Public Health of Shanghai Jiao Tong University approved the study. We obtained written informed consent from all participants following clarification of the study objectives and procedure, as well as the potential risks and benefits of participation.
: Not applicable.
: The authors declare that they have no competing interests.