Received: 31 March 2021
Accepted: 14 April 2021
First Online: 3 May 2021
: The welfare offices of the municipalities agreed to provide anonymized secondary data to the authors via a system company that had provided management software for the public assistance database to the municipality welfare offices. Informed consent was waived by the Research Ethics Committee of the Graduate School of Medicine of the University of Tokyo because of encrypted identification number. Further, the parents or legal guardians of those in the study population were provided opportunities to opt out of inclusion in each municipality. The study protocol was approved by the Research Ethics Committee of the Graduate School of Medicine of the University of Tokyo (Approval No: 11503). This study was carried out in accordance with STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines.
: Not applicable.
: Daisuke Nishioka received a research grant from Seseragi Foundation. Junko Saito, and Keiko Ueno declare no competing interests associated with this manuscript. Naoki Kondo conducted collaborative research with KITACOM, which provided the data used in the present paper. Naoki Kondo received a research fund and scholarship donation from KITACOM. These financial bodies had no discretion or involvement in our study protocol, analysis, interpretation of the results, or submission of this manuscript.