Funding for this research was provided by:
Ministry of Health, Labour and Welfare (H27-Policy-Designated-009, H27-Policy-Strategy-011)
Article History
Received: 7 June 2019
Accepted: 15 December 2019
First Online: 26 December 2019
Ethics approval and consent to participate
: This study was approved by The Tokyo Medical and Dental University ethics committee (approval number: M2000–788). The ethics committee approved that there was no need for formal consent to be participate to be obtained because the study design was retrospective and the data were anonymous.
: Not applicable.
: All authors have no competing interest to be disclosed.