Funding for this research was provided by:
National Natural Science Foundation of China (81473073)
Received: 13 December 2017
Accepted: 20 February 2019
First Online: 4 March 2019
Ethics approval and consent to participate
: The study was approved by Shanxi Medical University Ethics Committee (HX201201). We confirm that all methods in the current study were carried out in accordance with the guidelines of the Declaration of Helsinki. Each participant provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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