Funding for this research was provided by:
National Natural Science Foundation of China (81600601)
Received: 25 July 2019
Accepted: 15 November 2019
First Online: 25 November 2019
Ethics approval and consent to participate
: The study protocol was approved by the ethics committee of the Affiliated Hospital of Qingdao University.
: Individual informed consent was obtained from each participant.
: The authors declare that they have no competing interests.