Funding for this research was provided by:
BK21-Plus Education Program of Korea
Received: 8 March 2019
Accepted: 24 January 2020
First Online: 3 February 2020
Ethics approval and consent to participate
: This study was approved by the Seoul National University Bundang Hospital Institutional Review Board (IRB number: X-1809-493-902, approval date: 22 March 2017). The requirement for informed consent was waived as the NHIS-HEALS database is anonymized using strict confidentiality guidelines prior to distribution.
: Not applicable.
: The authors declare that they have no competing interests.