Article History
Received: 13 September 2019
Accepted: 17 February 2020
First Online: 22 February 2020
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Korea university hospital (IRB number: 2018AN0217). Permission to access National Health Insurance Service – National Sample Cohort data was granted by National Health Insurance Service chairman on 28th, September, 2018 (research management number: NHIS-2018-2-290). In order to ensure confidentiality in personal identification, the data used the in this study was organized in a way that assigns an identification number.
: Not applicable.
: The authors declare that they have no competing interests.