Funding for this research was provided by:
China Medical Board (CMB 13-160)
Shandong University Multidisciplinary Research and Innovation Team of Young Scholars (2020QNQT019)
Received: 31 May 2020
Accepted: 18 November 2020
First Online: 25 November 2020
Ethics approval and consent to participate
: All procedures performed in this study are in accordance with ethical standards of the Institutional Review Board at the School of Public Health at Shandong University (NO.20140201), and with the Declaration of Helsinki. Written informed consent was obtained from all participants before data collection.
: Not applicable.
: The authors declare that they have no competing interests.