Received: 8 March 2021
Accepted: 12 April 2021
First Online: 6 May 2021
: The NHIS data are de-identified by the Korean government [CitationRef removed]. These de-identified data are open to the public after completing a designated registration process for access. The study design was reviewed and approved by the Institutional Review Board of the Asan Medical Center (approval number: 2018-0971). Informed consent was also waived by the Institutional Review Board of the Asan Medical Center (approval number: 2018-0971). All methods were carried out in accordance with relevant guidelines and regulations.
: Not applicable.
: The authors declare that thy have no competing interests.