Funding for this research was provided by:
National Natural Science Foundation of China (81600760)
Received: 13 January 2018
Accepted: 29 January 2019
First Online: 20 February 2019
Ethics approval and consent to participate
: The research was approved by Peking University Third Hospital Medicine Ethics Committee (IRB00006761–2012046) and was conducted in accordance with the Declaration of Helsinki. Informed written consent was obtained from each participant.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.