Received: 5 August 2019
Accepted: 1 July 2020
First Online: 9 July 2020
Ethics approval and consent to participate
: The National Health Services Surveys received ethical approval from the National Statistics Bureau of China. Oral consent process was used for illiterate participants. All Participants gave oral consent to participate in the study. No individual identifiable data (name, address, phone number, etc.) were collected.
: Not Applicable.
: All authors contributed to this manuscript and have no conflicts interest.