Funding for this research was provided by:
Sichuan Science and Technology Program (2019YFS0274)
Text and Data Mining valid from 2020-01-02
Received: 29 July 2019
Accepted: 22 December 2019
First Online: 2 January 2020
Ethics approval and consent to participate
: The ethical approval of data collection was from the Biomedical Ethics Review Committee of Peking University (IRB00001052–11015). Every participant signed an informed consent before investigation, and their information were kept anonymous.
: No applicable.
: The authors declare that they have no competing interests.