Objective-To investigate the association between duration of overtime and t
he development of impaired fasting glucose (IFG) or type 2 diabetes mellitu
Methods-A cohort of 1266 Japanese male office workers aged 35-59 years and
free of IFG (fasting plasma glucose concentration 6.1-6.9 mmol/l), type 2 D
M (fasting plasma glucose concentration of 7.0 mmol/l or more or taking hyp
oglycaemic medication), history of diabetes, or medication for hypertension
were re-examined over 5 successive years after their initial examinations
Results-138 men developed IFG or type 2 DM during the 5736 person-years of
follow up. After controlling for potential predictors of diabetes, the rela
tive risks of IFG or type 2 DM, compared with those who worked <8.0 hours a
day, were 0.82 (95% confidence interval (95% CI) 0.54 to 1.26), 0.69 (95%
Cl 0.38 to 1.26), 0.63 (95% CI: 0.37 to 1.09), and 0.50 (95% Cl: 0.25 to 0.
98) for those who worked 8.0-8.9, 9.0-9.9, 10.0-10.9, and of 11.0 hours or
more a day, respectively (p for trend=0.020). 87 and 54 men developed IFG a
nd type 2 DM during the 5817 and 5937 person-years of follow up, respective
ly. The multivariate adjusted relative risks of IFG tended to decrease with
an increase in hours of overtime work a day, but did not reach significanc
e (p for trend=0.202). On the other hand, the multivariate adjusted relativ
e risks of type 2 DM significantly decreased with an increase in hours of o
vertime work a day (p for trend=0.014).
Conclusion-Longer overtime is a negative risk factor for the development of
IFG or type 2 DM in Japanese male office workers.