Received: 15 April 2022
Accepted: 11 July 2022
First Online: 17 July 2022
: CHARLS was approved by the Biomedical Ethics Review Committee of Peking University, and the ethical approval number was IRB00001052-11015. All procedures were in accordance with the ethical standards of the Helsinki Declaration. Participants provided informed consent before data collection.
: Not applicable.
: The authors declare no conflict of interest.