Funding for this research was provided by:
National Natural Science Foundation of China (71573068, 71333003)
Text and Data Mining valid from 2019-09-10
Received: 22 October 2018
Accepted: 28 August 2019
First Online: 10 September 2019
Ethics approval and consent to participate
: The NHSS was organized and administered by the National Health Commission of the People’s Republic of China. The institutional review board of the Chinese National Bureau of Statistics provided review and ethics approval of the survey. All respondents were read a statement that explained the purpose of the survey and provided verbal informed consent before interview.
: Not applicable.
: The authors declare that they have no competing interests.