Funding for this research was provided by:
National Natural Science Foundation of China (81273041)
Natural Science Foundation of Shanxi Province (201701D121146)
Received: 3 April 2019
Accepted: 22 July 2019
First Online: 29 July 2019
Ethics approval and consent to participate
: The study was approved by the Medical Ethics Committee of the Shanxi Medical University.
: Not applicable.
: The authors declare that they have no competing interests.