Funding for this research was provided by:
National Health Insurance Service (NHIS-2018-1-428)
Received: 17 January 2019
Accepted: 22 July 2019
First Online: 1 August 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of the National Health Insurance Service of the Ilsan Hospital and adhered to the tenets of the Declaration of Helsinki (NHIMC 2018–12-003). Written informed consent was waived as the data were de-identified in the database used.
: Not applicable.
: The authors declare that they have no competing interests.