Funding for this research was provided by:
Basic Science Research Program through the National Research Foundation of Korea (NRF-2017R1D1A1B03033382)
Received: 3 May 2019
Accepted: 24 May 2019
First Online: 31 May 2019
Ethics approval and consent to participate
: The NHIS-NSC data was fully anonymized for privacy protection. Due to the retrospective nature and use of de-identified data, this study was approved, and informed consent was waived by the Institutional Review Board of Bundang CHA Medical Center (CHAMC 2018-12-032).
: Not applicable.
: The authors declare that they have no competing interests.