Funding for this research was provided by:
National Natural Science Foundation of China (81703315, 81573250)
Received: 23 April 2017
Accepted: 6 March 2018
First Online: 14 March 2018
Ethics approval and consent to participate
: The NHSS 2008 was approved by the National Bureau of Statistics (license number: 2008 [CitationRef removed]). The NHSS is implemented by the NHFPC every five years, and the NHFPC has pledged to protect the privacy of respondents and to facilitate the anonymous analysis of the data according to article 14 of the third chapter of the Statistics Law of the People’s Republic of China. For these reasons, written consent was not required. The investigators read the informed consent statement written on the second page of the questionnaire and verbally asked for the interviewees’ permission. Once the interviewees or their caregivers or guardians (in the case of children) had verbally consented to participate in this study, the investigators would sign their own names at the beginning of the questionnaire.
: Not applicable
: The authors declare that they have no competing interests.
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