Funding for this research was provided by:
National Natural Science Foundation of China (31900561, 81702949)
the Natural Sciences of Foundation of Hunan Province (2018JJ3851)
the Scientific Research Fund Project of Hunan Provincial Health Commission (20201919)
the Huxiang Talent Aggregation Project from Hunan Provincial Science and Technology Department (2018RS3027)
Received: 18 May 2020
Accepted: 13 September 2020
First Online: 23 September 2020
Ethics approval and consent to participate
: The data obtained permission to download the research data file from the SEER database, which did not require further informed ethics approval and consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.