Funding for this research was provided by:
National Natural Science Foundation of China (31371272)
Received: 5 April 2019
Accepted: 14 July 2019
First Online: 24 July 2019
Ethics approval and consent to participate
: The study was permitted by the relevant ethics review board located at the Affiliated Hospital of Qingdao University, and according to the principles of the Declaration of Helsinki. All participants in this study presented their written informed consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.