Funding for this research was provided by:
Health and Labour Sciences Research Grants (H27-Rodo-Ippan-004)
Industrial Disease Clinical Research Grants (180701-01)
Received: 27 May 2019
Accepted: 27 January 2020
First Online: 4 February 2020
Ethics approval and consent to participate
: This study was approved by Kitasato University Medical Ethics Organization (No. B15–113). Informed consent was obtained from participants using the opt-out method. Kitasato University Medical Ethics Organization approved the use of opt-out consent.
: Not applicable.
: The authors declare that they have no competing interests.