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Work stress and overtime work: effects on cortisol, sleep, sleepiness and health
Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: Stockholm University, 2006. , 112 p.
Keyword [en]
work stress, overtime work, cortisol, sleep, sleepiness, fatigue, individual differences, within-subjects design, field study
National Category
Environmental Health and Occupational Health
Identifiers
URN: urn:nbn:se:kth:diva-86886ISBN: 91-7155-374-9 OAI: oai:DiVA.org:kth-86886DiVA: diva2:501133
Note
QC 20120305Available from: 2012-02-13 Created: 2012-02-13 Last updated: 2012-03-05Bibliographically approved
List of papers
1. Different levels of work-related stress and the effects on sleep, fatigue and cortisol
Open this publication in new window or tab >>Different levels of work-related stress and the effects on sleep, fatigue and cortisol
2005 (English)In: Scandinavian Journal of Work, Environment and Health, ISSN 0355-3140, E-ISSN 1795-990X, Vol. 31, no 4, 277-285 p.Article in journal (Refereed) Published
Abstract [en]

Objectives The aim of the study was to relate different levels of work stress to measures of sleep and the diurnal pattern of salivary cortisol and subjective sleepiness.

Methods Thirty-four white-collar workers participated under two different conditions. One workweek with a relatively high stress level (H) and one with a lower stress level (L) as measured through self-rated stress during workdays. The workers wore activity monitors, filled out a sleep diary, gave saliva samples (for cortisol), and rated their sleepiness and stress during one workday and one free day.

Results During the week with stress the number of workhours increased and total sleep time decreased. Sleepiness showed a significant interaction between weeks and time of day, with particularly high levels towards the evenings of the stress week. Cortisol also showed a significant interaction, with a more flattened pattern, probably due to increased evening levels during the stress week. Stress (restlessness) at bedtime was significantly increased during the stress week.

Conclusion The results demonstrate that a workweek with a high workload and much stress increases sleepiness and workhours, impairs sleep, and affects the pattern of diurnal cortisol secretion.

Keyword
actigraphy, sleepiness, workhours
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:kth:diva-86889 (URN)10.5271/sjweh.883 (DOI)000231618800005 ()
Note
QC 20120305Available from: 2012-02-13 Created: 2012-02-13 Last updated: 2017-12-07Bibliographically approved
2. Overtime work and its effects on sleep, sleepiness, cortisol and blood pressure in an experimental field study
Open this publication in new window or tab >>Overtime work and its effects on sleep, sleepiness, cortisol and blood pressure in an experimental field study
2006 (English)In: Scandinavian Journal of Work, Environment and Health, ISSN 0355-3140, E-ISSN 1795-990X, Vol. 32, no 4, 318-327 p.Article in journal (Refereed) Published
Abstract [en]

Objectives Previous studies of long workhours and their effects on stress, sleep, and health show inconclusive results. This inconclusiveness may be partly due to methodological problems such as the use of between-group designs or comparisons before and after reorganizations. In addition, stress is usually a confounder. A within-person design was used to examine the effects of working 8- or 12-hour shifts in the absence of additional stress.

Methods In an experimental field study, 16 white-collar workers [9 women, mean age 45.9 (SD 15) years] undertook one workweek with normal workhours (8 hours) and 1 week of overtime with 4 extra hours of regular worktasks (12 hours). The participants wore actigraphs, rated sleepiness (Karolinska Sleepiness Scale) and stress throughout the day, and rated workload and how exhausted they felt. Saliva samples were collected on Mondays and Thursdays for cortisol analysis. On these days, ambulatory heart rate and blood pressure were also measured for 24 hours.

Results Overtime was associated with higher levels of exhaustion. Sleepiness showed a significant interaction between conditions, with higher levels at the end of the workweek featuring overtime. Total sleep time was shorter in the overtime week. There were no significant differences between ratings of stress and workload. Cortisol showed a circadian variation but no main effect of condition.

Conclusions One week of overtime work with a moderate workload produced no main effects on physiological stress markers. Nevertheless, sleep was negatively affected, with shorter sleeps during overtime work and greater problems with fatigue and sleepiness.

Keyword
fatigue, stress, within-person design, workhours
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:kth:diva-86888 (URN)10.5271/sjweh.1016 (DOI)000240093500009 ()
Note
QC 20120305Available from: 2012-02-13 Created: 2012-02-13 Last updated: 2017-12-07Bibliographically approved
3. Individual differences in the diurnal cortisol response to stress
Open this publication in new window or tab >>Individual differences in the diurnal cortisol response to stress
2004 (English)In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 21, no 6, 913-922 p.Article in journal (Refereed) Published
Abstract [en]

The objectives of this study were to explore individual differences associated with diverse reactions in cortisol secretion under different stress levels. This study was part of a larger project concerning working hours and health. Thirty-four whitecollar workers participated under two different conditions; one work week with a high stress level (H) and one with a lower stress level (L) as measured through self-rated stress during workdays. Based on the morning cortisol concentration during a workday subjects were divided into two groups. One group consisted of subjects whose morning level of cortisol increased in response to the high-stress week, compared to their morning levels in the low-stress condition (Group 1). The other group consisted of subjects whose morning cortisol response was the opposite, with a lower level under the high stress condition (Group 2). Subjects wore actiwatches, completed a sleep diary, and rated their sleepiness and stress for one work week in each condition, i.e., high and low stress. Saliva samples for measures of cortisol were collected on a Wednesday. Group 2 reported higher workload, fatigue, and exhaustion during both weeks. Since there were no differences in perceived stress, neither within nor between groups, the data indicate that there are other factors influencing morning cortisol. The results suggest that one component modulating the cortisol response might be the level of exhaustion, probably related to work overload. Higher levels of stress in exhausted individuals might suppress morning cortisol levels.

Keyword
morning cortisol, stress, exhaustion, individual differences, occupation medication
National Category
Environmental Health and Occupational Health
Identifiers
urn:nbn:se:kth:diva-86887 (URN)10.1081/CBI-200035937 (DOI)000226044700009 ()
Note

QC 20120305

Available from: 2012-02-13 Created: 2012-02-13 Last updated: 2017-06-15Bibliographically approved

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