Funding for this research was provided by:
Grant-in-Aid for Scientific Research
Received: 27 June 2017
Accepted: 31 January 2018
First Online: 9 February 2018
Ethics approval and consent to participate
: The ethics committee of the Hamamatsu University School of Medicine approved the study. Written informed consent was obtained from the parents of all of the participants.
: Not applicable.
: The authors declare that they have no competing interests.
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