Received: 26 June 2020
Accepted: 3 December 2020
First Online: 4 January 2021
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of the Ningxia People’s Armed Police Corps Hospital and in accordance with the standards of the National Research Council. Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.