Received: 29 October 2019
Accepted: 17 March 2020
First Online: 30 March 2020
Ethics approval and consent to participate
: This study was approved by the Ethical Committee Board at the School of Public Health, Jilin University (Approval No: 2018-03-05). Each participant also provided written informed consent to this study.
: Consent for publication obtained from participants.
: The authors declare that they have no competing interests.