Text and Data Mining valid from 2019-11-16
Received: 10 August 2019
Accepted: 25 October 2019
First Online: 16 November 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board (IRB) of Samsung Medical Center (IRB number: SMC 2017-07-142). An informed consent exemption was granted by the IRB because all data provided by the NHIS to researchers were de-identified.
: Not applicable.
: The authors declare that they have no competing interests.