Funding for this research was provided by:
the grants from the Ministry Science and Technology of China (2016YFC0901205, 2016YFC0901200)
research grant from Health and Family Planning Commission of Sichuan Province (16129)
Text and Data Mining valid from 2019-12-01
Received: 15 September 2019
Accepted: 21 November 2019
First Online: 2 December 2019
Ethics approval and consent to participate
: The study was approved by the ethics committee of the Affiliated Hospital of Southwest Medical University. Written informed consent was obtained before the data collection and analysis.
: Not applicable.
: The authors declare that they have no competing interests.