Article History
Received: 23 June 2021
Accepted: 17 August 2021
First Online: 23 August 2021
Declarations
:
: None.
: Ethics approval for CHARLS was obtained from the Biomedical Ethics Review Committee of Peking University (IRB00001052-11015).
: All the participants have completed written informed consent.
: The authors affirm that human research participants provided informed consent for publication.