Received: 14 August 2020
Accepted: 7 December 2020
First Online: 6 January 2021
Ethics approval and consent to participate
: This study protocol was approved by the Institutional Review Board (IRB) of Asan Medical Center (IRB No. 2020 − 0649). The requirement for informed consent was waived because the KNHIS database was constructed after anonymization according to strict confidentiality guidelines. Administrative permission to access the National Health Information Database was obtained from the National Health Insurance Sharing Service (NHIS-2017-2-336).
: Not applicable.
: The authors declare that they have no competing interests.