Text and Data Mining valid from 2019-11-06
Received: 15 May 2019
Accepted: 15 October 2019
First Online: 6 November 2019
Ethics approval and consent to participate
: This study was conducted in accordance of the Declaration of Helsinki and approved by the Institutional Review Board of the Sapporo Medical University School of Medicine (approval number: 272–94). Written informed consents were obtained from all participants.
: Not applicable.
: The authors declare that they have no competing interests.