Funding for this research was provided by:
National Research Foundation of Korea (2018R1D1A1B07047587)
Korea University Guro Hospital ‘KOREA RESEARCH-DRIVEN HOSPITALS’ Grant (O1905461)
Received: 16 February 2020
Accepted: 5 June 2020
First Online: 13 June 2020
Ethics approval and consent to participate
: The Institutional Review Board (IRB) of Korea University approved this study (IRB file number 2019GR0329). An informed consent exemption was granted by the IRB because the KNHIS provided the researchers with anonymous, de-identified data only.
: Not applicable.
: The authors declare that they have no competing interests.