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Dahlgren A, Kecklund G, Åkerstedt T. Different levels of work-related stress and the effects on sleep, fatigue and cortisol. Scand J Work Environ Health 2005;31(4):277-285.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. ConclusionsThe 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.

Dahlgren A, Kecklund G, Åkerstedt T. Overtime work and its effects on sleep, sleepiness, cortisol and blood pressure in an experimental field study. Scand J Work Environ Health 2006;32(4):318-327.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 withinperson 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.

Background Burnout is common among nurses and midwives. We examined whether an early career episode of burnout has long-term consequences on; a) cognitive functions, b) symptoms of depression, and/or c) insomnia for nurses a decade after graduation. Methods Symptoms of burnout were investigated in an observational longitudinal study of three national cohorts of registered nurses (RNs). Nursing students were recruited from all 26 of Sweden's nursing programs. Burnout was subsequently measured through annual assessment over the first three years post graduation, with one long-term follow-up 11–15 years after graduation. A total of 2474 nurses (62%) consented to participate at follow-up. Burnout was measured using items from the Oldenburg Burnout Inventory, cognitive function by a study specific instrument, depressive symptoms by the Major Depression Inventory, and sleep problems using items from the Karolinska Sleep Questionnaire. We used logistic regression to identify factors associated with consequences of early career burnout, adjusting for concurrent levels at follow up. Findings The prevalence of nurses reporting high levels of burnout symptoms at least one of the first three years of working life was 299 (12·3%). High levels of burnout symptoms in early working life were significantly related to more frequent symptoms of cognitive dysfunction, depression, and impaired sleep a decade later when taking current burnout levels into account. After controlling for both current symptoms of burnout and the other outcome variables, nurses with early career burnout still reported more frequent problems with cognitive functions and sleep but not depression. Interpretation The results of this study show that the detrimental processes caused by overwhelming or chronic stress start early on in nurses’ careers and thus preventive efforts should preferably be introduced early on (e.g. as part of nursing education and onboarding programs). Funding AFA Insurance Grant [number 150284].

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