Article History
Received: 9 December 2017
Accepted: 7 February 2018
First Online: 12 March 2018
Ethics approval and consent to participate
: Each participant included in this study signed a written informed consent form before taking the survey. Ethics approval for the data collection in CHARLS was obtained from the Biomedical Ethics Review Committee of Peking University (IRB00001052-11015). Ethics approval for the use of CHARLS data was obtained from the University of Newcastle Human Research Ethics Committee (H-2015-0290).
: All authors approved the final manuscript for submission and gave consent for publication.
: The authors declare that they have no competing interests.
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