Original ArticlePredictors of shift work disorder among nurses: a longitudinal study
Introduction
Estimates suggest that approximately 20% of workers in Europe are employed in some form of shift work that involves night work [1]. Shift work is associated with a wide range of health problems [2], [3]. In work schedules that include night work, sleep problems are among the most frequently reported health problems [4], [5]. The most common sleep problems among night shift workers are sleep onset and maintenance difficulties, reduced sleep duration, and excessive sleepiness during work [5]. For Norwegian nurses, it is common to work rotating shifts, which is a work schedule that could involve morning, evening, and night shifts within the same work week. This is reported to lead to insufficient sleep duration [6], and night work is reported to be the most important cause of long-term stress and fatigue [7]. Nurses in rotating shifts have reported more mental health problems compared to nurses working non-rotating shifts [8], and associations between shift work, anxiety and depression have also been shown [9]. In a recent Norwegian study, nurses working in intensive care units were found to report poorer sleep and higher levels of sleepiness, fatigue, anxiety, and depression compared to Norwegian norm groups [10]. However, results linking shift work and mental health are inconsistent; anxiety and depression were for example not associated with night work in a cross sectional study of Norwegian nurses [11].
Shift work disorder (SWD) is a circadian rhythm sleep disorder characterized by excessive sleepiness and complaints of insomnia related to the work schedule [12]. The diagnostic criteria for SWD are described in the second edition of the International Classification of Sleep Disorders (ICSD-2) and include the following four criteria: (1) Complaint of insomnia or excessive sleepiness temporally associated with a recurring work schedule that overlaps the usual time for sleep, (2) symptoms must be associated with the shift work schedule and present over the course of at least one month, (3) circadian and sleep-time misalignment as demonstrated by sleep log or actigraphical monitoring for 7 days or more, and finally (4) sleep disturbance is not explainable by another sleep disorder, a medical or neurological disorder, mental disorder, medication use or substance use disorder [13].
Varying prevalences of SWD have been reported in cross-sectional studies, ranging from 14.5% among police officers working nights [14], 23.3% among oil rig workers [15], 24.4% among shift working nurses [16], 32.1% among Australian night workers [17], and up to 44.3% among Norwegian nurses in rotating shift work [18]. SWD is a relatively new diagnosis, and there is uncertainty and discussion about its operationalization, prevalence, consequences, and treatment [19]. At present, few studies have used standardized questions to measure SWD which seems to be underestimated in clinical settings. Epidemiological data on SWD are scarce [20]. One limitation of previous research on SWD is that the studies are based on cross-sectional design which prevent conclusions concerning directionality and possible cause–effect relationships related to the development and consequences of SWD.
To address this limitation, the main aim of the present study was to explore predictors of SWD among Norwegian shift working nurses using longitudinal data. We also aimed to assess the prevalence of SWD among Norwegian nurses at baseline and follow-up.
Section snippets
Procedure and participants
The data were collected from an on-going longitudinal cohort study “SUrvey of Shift work, Sleep and Health (SUSSH)” that was initiated in 2008/2009. A sample of 5400 nurses was randomly selected from the Norwegian Nurses Organization's membership roll which includes most of the nurses in Norway. Survey questionnaires have been sent to this sample annually and this study presents findings from the first (2008/2009 = baseline) and the third wave (2011 = follow-up) of the survey.
The sample
Demographics
At baseline (n = 1533), the mean age of the nurses was 33 years, range 21–63. Among the whole sample, 76.3% worked in somatic hospital departments, 13.5% in psychiatric departments, 3.5% in nursing homes, 3.7% in home care services, and 2.1% in other work places, respectively. The mean hours worked per week were 33.9 with a distribution of 2.8% working <50% position, 28.6% working between 50% and 75% of full time position, 13.4% working between 76% and 90% of full time position, and 55.2%
Discussion
Having SWD at baseline, use of exogenous melatonin, use of bright light therapy, number of nights worked last year, sleepiness score, and depression score were all found to be predictors of SWD among Norwegian nurses. In addition, quitting night shifts from baseline to follow-up decreased the risk of SWD at follow-up. Interestingly, there was overall a significant reduction in the prevalence of shift work disorder (SWD) from 35.7% at baseline to 28.6% at follow-up.
Measured at baseline, the
Conclusion
Several factors measured at baseline like reporting SWD, use of exogenous melatonin, use of bright light therapy, number of nights worked last year, sleepiness score, and depression score were found to be significant predictors of SWD at follow-up. In addition, quitting night work between baseline and follow-up was significantly associated with a decreased risk of SWD at follow-up, suggesting that night work may be a major cause of SWD. There was a significant reduction in the SWD prevalence
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2014.07.014.
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