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 examination
s. Men in whom borderline hypertension and hypertension were found during r
epeated surveys were defined as incidental cases of borderline hypertension
Main results-336 and 88 men developed hypertension above the borderline lev
el and definite hypertension during the 3940 and 4531 person years, respect
ively. After controlling for potential predictors of hypertension, the rela
tive 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 <greater than or equal to> 11.0 hours per da
y. The relative risk for definite hypertension, compared with those who wor
ked < 8.0 hours per day, was 0.33 (95% CI: 0.11, 0.95) for those who worked
<greater than or equal to> 11.0 hours per day. The multi-variate 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 inc
reased. From the multiple regression analyses, working hours per day remain
ed as an independent negative factor for the slopes of systolic blood press
ure, DBP, and MABP.
Conclusions-These results indicate that long working hours are negatively a
ssociated with the risk for hypertension in Japanese male white collar work