Received: 18 May 2022
Accepted: 20 September 2022
First Online: 5 October 2022
: Ethical approval for all the CHARLS waves was granted from the Institutional Review Board (IRB) of Peking University (IRB00001052-11015). Informed consent was obtained from all participants, including legal representatives of illiterate participants. All methods were carried out in accordance with relevant guidelines and regulations.
: Not applicable.
: The authors declare that they have no competing interests.