Relationship between overtime work hours and cardio-ankle vascular index (CAVI): a cross-sectional study in Japan.

OBJECTIVES The purpose of this research was to evaluate the relationship between overtime work hours and CAVI, a new index of arterial stiffness. METHODS We measured CAVI of Japanese workers (3,862 men) aged 26 to 59 years. Simultaneously, we obtained information on their monthly overtime work hours for the past few months using a self-administered questionnaire, with responses divided into five groups: <45, ≥45 and <60, ≥60 and <80, ≥80 and <100 and ≥100 hours/month. We calculated the odds ratios of CAVI≥9.0 for each group of overtime work hours. RESULTS In the full sample, there was no significant association between the average CAVI and overtime work hours. Taking<45 overtime hours/month as the reference category, the odds ratios of CAVI≥9.0 were as follows: OR=1.11, 95% CI=0.73-1.69 (≥45 and <60 hours/month); OR=0.92, 95% CI=0.48-1.76 (≥60 and <80 hours/month); OR=1.50, 95% CI=0.50-4.49 (≥80 and <100 hours/month); and OR=2.65, 95% CI=0.82-8.54 (≥100 hours/month). However, for workers in their 50 s, the odds ratio of CAVI≥9.0 was significantly higher among subjects with≥100 hours/month than among those with<45 hours/month (OR=4.26, 95% CI=1.2-15.1) CONCLUSIONS: The present study suggests that CAVI is more likely to be 9.0 or higher in workers in their 50 s when they work≥100 hours of overtime per month.