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Work stress and overtime work
Effects on cortisol, sleep, sleepiness and health
Stockholm universitet 2006, 71 s. ISBN 9171553749 (del af doktorsafhandling)
Bogomtale fra forlaget.
In Sweden the National Bureau of Statistics has reported an increase in stress-related
disorders and sleep problems since the mid-1990’s. They also report that the number of hours
of overtime worked has increased. Previous research on work-related stress and overtime
work has demonstrated associations with altered physiological arousal, increased risk for
stress related diseases, shorter sleep, greater fatigue and impaired performance. However,
there is a lack of knowledge on the effects within individuals. The general aim of the thesis
was to investigate the effect of overtime work and increased work stress on sleep, the diurnal
pattern of cortisol, sleepiness and subjective stress in a within-subject design. In addition, it
examined individual differences in the diurnal cortisol response to stress.
We used a combination of methods – questionnaires, sleep and wake diaries, objective
measures of sleep, stress hormones (salivary cortisol) and ambulatory measures of heart rate
and blood pressure. Studies followed office workers during two different conditions of (I)
high/low work stress and (II) overtime work respectively. The individual differences in the
cortisol response to stress from study I prompted study III. In this study we examined two
groups that showed different cortisol responses to stress.
In conclusion, the results (I) demonstrated that a week with higher workload and stress affects
physiological stress markers such as cortisol, and is associated with increased sleepiness and
problems of unwinding at bedtime, shorter sleep duration and longer work hours. Furthermore
(II) overtime work, under conditions of relatively low workload, was shown to be associated
with modest effects on physiological markers of arousal. More pronounced effects were found
on sleep and fatigue, with greater problems during overtime work. Study III indicated that
individual differences in cortisol response to stress maybe related to fatigue and exhaustion.