Funding for this research was provided by:
National Natural Science Funds of China (71603166, 71673187)
Received: 15 October 2018
Accepted: 14 May 2019
First Online: 23 May 2019
Ethics approval and consent to participate
: The Ethics Committee of Shanghai Jiao Tong University School of Public Health approved this study. Before enrolment, all participants provided written informed consent after being informed of the objectives and procedures of the study, and potential risks and benefits of participation.
: Not applicable.
: The authors declare that they have no competing interests.
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