Wang, Yanan
Li, Zhen
Fu, Chang
Article History
Received: 27 April 2021
Accepted: 7 October 2021
First Online: 18 October 2021
Declarations
:
: Ethical approval for this study was not required because it was based exclusively on the public available data, CHARLS, and the study subjects were not directly approached. All study participants gave their informed consent for inclusion before they participated in the study. All methods in the present study were carried out in accordance with relevant guidelines and regulations.
: Not applicable.
: The author(s) declared no conflict of interest.