Received: 25 November 2018
Accepted: 18 October 2019
First Online: 8 November 2019
Ethics approval and consent to participate
: The ethics committee at Kobe University Graduate School of Medicine exempted this study from the requirement for approval since the study deals with data in the public domain and does not involve individual human subjects. Likewise, we did not obtain informed consent from anybody regarding this study.
: Not applicable.
: The authors declare that they have no competing interests.