Funding for this research was provided by:
Natural Science Foundation of Shandong Province (ZR2016GQ02)
Text and Data Mining valid from 2020-05-11
Received: 31 July 2019
Accepted: 4 May 2020
First Online: 11 May 2020
Ethics approval and consent to participate
: This study was conducted in accordance with the Declaration of Helsinki. The study protocol was approved by the ethics committee of School of Health Care Management, Shandong University, China. All participants were informed of the research aims prior to participation, and informed consent forms were signed by participants themselves, or by their relatives representing participants who could not sign their own names.
: Not applicable.
: The authors declare that they have no competing interests.