Received: 23 March 2019
Accepted: 2 April 2020
First Online: 24 May 2020
Ethics approval and consent to participate
: A secondary analysis of existing data with human subjects may be exempted from examination by the competent institutional committee according to Korean law (Bioethics and Safety Act). Therefore, this study was approved for approved for exemption consent by the Institutional Review Board of the Seoul National University (No. E1811/002–002).
: Not Applicable.
: The authors declare that they have no competing interests.