Funding for this research was provided by:
Japan Society for the Promotion of Science KAKENHI (17K15850)
Received: 15 February 2019
Accepted: 23 April 2019
First Online: 30 May 2019
Ethics approval and consent to participate
: The study protocol was reviewed and approved by the Ethics Committee of Niigata University (approval numbers 2012–1640, 2015–2140, 2017–0054). Written informed consent was obtained from participants. The study adhered to the tenets of the Declaration of Helsinki.
: Not applicable
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.