Association of Work Situation With Cardiovascular Disease Mortality Risk Among Working-Age Japanese Men - A 20-Year Follow-up of NIPPON DATA90.

Background: Several cohort studies have demonstrated an association between socioeconomic status (SES) and health outcomes in Japan. As long-term employment is common in Japan, the size of the company may be related to cardiovascular disease (CVD) mortality risk. We examined the association of employment conditions with CVD mortality risk among working-age Japanese men (30-59 years, n=2,091).

Methods and results: We used 20-year follow-up data from NIPPON DATA90, for which baseline data were obtained from the 4th National Survey on Circulatory Disorders in 1990. Participants were classified into 4 groups: 3 strata for indefinite-term employees according to company size (large company/public office, moderate-sized, or small), and the self-employed/administrator group. Multivariable-adjusted hazard ratios (HRs) were adjusted for age, lifestyle, and CVD risk factors. Smokers were more common, habitual exercise was less common, and the average systolic blood pressure was higher among indefinite-term employees of small companies compared with employees at large companies/public offices. There was no significant difference in the total CVD mortality risk between indefinite-term employees and self-employed/administrator participants. The age-adjusted HR (95% confidence interval) for total CVD using indefinite-term employees of large companies/public office as a reference was 2.53 (1.12, 5.69) for employees of small companies.

Conclusions: Working as an indefinite-term employee at a small company in Japan was significantly associated with elevated risk of CVD mortality among Japanese men.