Funding for this research was provided by:
National Research Foundation of Korea (NRF-2016R1A2B4011662, NRF-2012M3A9C4048762)
Ministry of Health and Welfare (HI14C2686, HI14C2686010116)
Received: 16 March 2017
Accepted: 8 January 2018
First Online: 22 February 2018
Ethics approval and consent to participate
: The purpose of the study was carefully explained to all participants, and written consent was obtained prior to their participation. The protocol was approved by the Institutional Review Board of Yonsei University and Yonsei University Severance Hospital in accordance with the Helsinki Declaration.
: Not applicable
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.