Funding for this research was provided by:
National Natural Science Foundation of China (72004002)
Received: 29 January 2021
Accepted: 3 March 2021
First Online: 12 March 2021
: The study protocol had been reviewed and approved by Anhui Medical University Biomedical Ethics Committee (ref: 20200936). This approved protocol clearly states: (a) participation and withdrawal from the study is voluntary; (b) at the beginning of recruitment, a consent from (Additional file InternalRef removed) will be signed (for those who are literate) or ticked (for those who are illiterate) by the participants; and (c) confidentiality of all informant information is strictly enforced.
: Not applicable.
: The authors declare that they have no competing interests.