Funding for this research was provided by:
Innovative Research Group Project of the National Natural Science Foundation of China (71403148)
Received: 2 July 2020
Accepted: 7 October 2020
First Online: 11 December 2020
Ethics approval and consent to participate
: This study was conducted according to the guideline proposed in the World Medical Association of Helsinki, and the ethical approval was obtained from the Ethics Review Board of the School of Public Health, Shandong University (Reference No. 20140301). Informed consent was obtained from all participants prior to questionnaire administration.
: All named authors have contributed substantially to the manuscript and have approved the submitted copy.
: The author reports no conflicts of interest in this work.