Funding for this research was provided by:
Cabinet Office, Government of Japan (2015-PM16-02-01)
Text and Data Mining valid from 2019-03-14
First Online: 14 March 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: The current study was waived for ethical approval because it uses the anonymized secondary data of an ethically approved occupational cohort study.