Funding for this research was provided by:
National Natural Science Foundation of China (81571756)
Article History
Received: 15 November 2020
Accepted: 8 February 2021
First Online: 7 March 2021
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: This study including human participants has been performed in accordance with the ethical standards laid down in the Declaration of Helsinki and its later amendments.
: Ethics approval for the data collection in CHARLS was obtained from the Biomedical Ethics Review Committee of Peking University (IRB00001052-11015).
: Each participant included in this study signed a written informed consent form before taking part in the survey.