Received: 11 November 2019
Accepted: 11 May 2020
First Online: 19 May 2020
Ethics approval and consent to participate
: We used publicly-available datasets from the official CHNS website (ExternalRef removed). Hence, the need for ethics approval was waived by the Institutional Review Board of Wuhan University. The CHNS provides respondents guarantees of their privacy and confidentially. All participants provided written informed consent. Details about the study design are available elsewhere [CitationRef removed].
: Not applicable.
: The authors declare that they have no competing interests.