Funding for this research was provided by:
National Natural Science Foundation of China (81573260)
Text and Data Mining valid from 2018-07-11
Received: 11 June 2018
Accepted: 3 July 2018
First Online: 11 July 2018
Ethics approval and consent to participate
: Ethical approval for the study was obtained from the Ethics Committee of Xiangya School of Public Health, Central South University (No. XYGW-2017-02). All participants will provide informed consent online prior to commencing the study.
: Not applicable.
: Guoqing Hu is an Associate Editor for BMC Public Health, none of the other authors have any competing interests.
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