Funding for this research was provided by:
National Natural Science Foundation of China (81102196)
Doctoral Fund of Ministry of Education of China (20090181120019)
Text and Data Mining valid from 2019-04-17
Received: 17 December 2018
Accepted: 8 April 2019
First Online: 17 April 2019
Ethics approval and consent to participate
: The study protocol was approved by the West China fourth Hospital of Sichuan University (West China School of Public Health).
: Not applicable
: The authors declare that they have no competing interests.
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