Long working hours and risk for hypertension in Japanese male white collar workers

Abstract

Study objective - To evaluate the association of long working hours with the risk for hypertension. Design - A five year prospective cohort study. Setting - Work site in Osaka, Japan. Participants - 941 hypertension free Japanese male white collar workers aged 35-54 years were prospectively examined by serial annual health examinations. Men in whom borderline hypertension and hypertension were found during repeated surveys were defined as incidental cases of borderline hypertension and hypertension. Main results - 336 and 88 men developed hypertension above the borderline level and definite hypertension during the 3940 and 4531 person years, respectively. After controlling for potential predictors of hypertension, the relative risk for hypertension above the borderline level, compared with those who worked < 8.0 hours per day, was 0.63 (95% confidence intervals (CI): 0.43, 0.91) for those who worked 10.0-10.9 hours per day and 0.48 (95% CI: 0.31, 0.74) for those who worked ≥ 11.0 hours per day. The relative risk for definite hypertension, compared with those who worked < 8.0 hours per day, was 0.33 (95% CI: 0.11, 0.95) for those who worked ≥ 11.0 hours per day. The multivariate adjusted slopes of diastolic blood pressure (DBP) and mean arterial blood pressure (MABP) during five years of follow up decreased as working hours per day increased. From the multiple regression analyses, working hours per day remained as an independent negative factor for the slopes of systolic blood pressure, DBP, and MABP. Conclusions - These results indicate that long working hours are negatively associated with the risk for hypertension in Japanese male white collar workers.