Received: 29 February 2020
Accepted: 30 June 2020
First Online: 6 July 2020
Ethics approval and consent to participate
: The study protocol was reviewed and approved by the Ethics Committee on Research of Human Subjects at Tohoku University Graduate School of Medicine (approval number: 2013–1-564). All participants gave informed consent to participate in this study. Parental/guardian consent was also obtained because the participants were younger than 16 years of age. Written informed consent was obtained from all the participants and parents/guardians.
: Not applicable.
: The authors declare no potential conflicts of interest.