Funding for this research was provided by:
Ministry of Health, Labour and Welfare
Ministry of Education, Culture, Sports, Science and Technology
Japan Agency for Medical Research and Development
Received: 30 November 2017
Accepted: 26 June 2018
First Online: 4 July 2018
Ethics approval and consent to participate
: The study was approved by the Institutional Review Board of The University of Tokyo (approval number: 3501). Because of the anonymous nature of the data, the need for informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.
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