Participants and methods
Participants
The study participants were employees of a factory that produces zippers and aluminum sashes in Toyama Prefecture,Japan. Detailed information on the study population has been reported previously [16–19]. The Industrial Safety and Health Law in Japan requires that employers
provide annual health examinations for all employees. A test for diabetes mellitus was conducted during annual medical examinations between 2003 and 2010. In 2003, 2,275 (89 %) of 2,543 male employees aged 35–55 years received health examinations and responded to the diet