Text and Data Mining valid from 2019-01-29
Received: 28 October 2018
Accepted: 12 January 2019
First Online: 29 January 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in this study involving human participants were accodance with the ethical approval.
: Ethical approval was obtained from the Ethics Committee of the University of Tokyo (No. 16-188).
: All participants gave written or oral informed consent.