Funding for this research was provided by:
National Natural Science Foundation of China (41801306, 41871140)
Guangdong Province Introduction of Innovative R&D Team (2017ZT07X355)
Innovation and Technology Commission - Hong Kong (City U11666716)
Text and Data Mining valid from 2019-08-02
Received: 23 May 2019
Accepted: 26 July 2019
First Online: 2 August 2019
Ethics approval and consent to participate
: This study is a secondary analysis of the de-identified CHARLS public data. The Medical Ethics Committee of Peking University granted the current study exemption from review. All respondents were informed about the procedure of the study and the written informed consent was obtained.
: Not applicable.
: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.