Received: 7 July 2021
Accepted: 1 March 2022
First Online: 28 April 2022
: The CHARLS is approved by by the Biomedical Ethics Review Committee of Peking University, and all participants provide informed consent. The NHANES is approved by the National Center for Health Statistics Research Ethics Review Board, and all participants provide informed consent. The study methodology was carried out following relevant guidelines and regulations.
: Not applicable.
: The authors declare that they have no competing interests.