Funding for this research was provided by:
Received: 26 December 2020
Accepted: 18 April 2021
First Online: 3 May 2021
: This study was approved by the Institutional Review Board of the Korea University (IRB: KUIRB-17-EX-257-A-1). Informed consent was waived because the data were de-identified before the analysis.
: Not applicable.
: The authors declare that they have no competing interests.