Funding for this research was provided by:
Beijing Municipal Social Science Foundation (16SRB015)
Received: 5 June 2020
Accepted: 31 August 2020
First Online: 17 September 2020
Ethics approval and consent to participate
: This study was approved by the Medical Ethics Committee of Capital Medical University, Beijing, China. Written informed consent was obtained from each participant involved in this study. All participant information was kept confidential.
: Not applicable.
: The authors declare that they have no competing interests.