Funding for this research was provided by:
Japanese Ministry of Health, Labour and Welfare (Research Grant (Gan-taisaku-ippan-012)
Received: 31 March 2019
Accepted: 16 August 2019
First Online: 11 September 2019
Ethics approval and consent to participate
: The medical ethics committee of Juntendo University informed us that ethical approval and consent was not required and because the data were existing data that were anonymous and impossible to concatenate, and no associated correspondence table exists, according to national guidelines [CitationRef removed].
: Not applicable.
: The authors declare that they have no competing interests.