Working hours and risk of acute myocardial infarction and stroke among middle-aged japanese men: The Japan public health center-based prospective study cohort II

Background: Evidence from prospective cohort studies regarding the relationship between working hours and risk of cardiovascular disease is limited Methods and Results: The Japan Public Health Center-Based Prospective Study Cohort II involved 15,277 men aged 40-59 years at the baseline survey in 1993. Respondents were followed up until 2012. During the median 20 years of follow up (257,229 personyears), we observed 212 cases of acute myocardial infarction and 745 stroke events. Cox proportional hazards models adjusted for sociodemographic factors, cardiovascular risk factors, and occupation showed that multivariable-adjusted hazard ratios (HRs) associated with overtime work of ≥11h/day were: 1.63 (95% confidence interval [CI] 1.01-2.63) for acute myocardial infarction and 0.83 (95% CI 0.60-1.13) for total stroke, as compared with the reference group (working 7 to <9 h/day). In the multivariable model, increased risk of acute myocardial infarction associated with overtime work of ≥11 h/day was more evident among salaried employees (HR 2.11, 95% CI 1.03-4.35) and men aged 50-59 years (HR 2.60, 95% CI 1.42-4.77). Conclusions: Among middle-aged Japanese men, working overtime is associated with a higher risk of acute myocardial infarction.