Abstract
PurposeAlthough shift work disorder (SWD) affects a major part of the shift working population, little is known about its manifestation in real life. This observational field study aimed to provide a detailed picture of sleep and alertness among shift workers with a questionnaire-based SWD, by comparing them to shift workers without SWD during work shifts and free time.MethodsSWD was determined by a questionnaire. Questionnaires and 3-week field monitoring, including sleep diaries, actigraphy, the Karolinska Sleepiness Scale (KSS), EEG-based sleep recordings, and Psychomotor Vigilance Tasks (PVT), were used to study 22 SWD cases and 9 non-SWD workers.ResultsThe SWD group had a shorter subjective total sleep time and greater sleep debt before morning shifts than the non-SWD group. Unlike the non-SWD group, the SWD group showed little compensatory sleep on days off. The SWD group had lower objective sleep efficiency and longer sleep latency on most days, and reported poorer relaxation at bedtime and sleep quality across all days than the non-SWD group. The SWD group’s average KSS-sleepiness was higher than the non-SWD group’s sleepiness at the beginning and end of morning shifts and at the end of night shifts. The SWD group also had more lapses in PVT at the beginning of night shifts than the non-SWD group.ConclusionsThe results indicate that SWD is related to disturbed sleep and alertness in association with both morning and night shifts, and to less compensatory sleep on days off. SWD seems to particularly associate with the quality of sleep.
Highlights
In the European Union, 21% of the workforce do some form of shift work (Eurofound 2017) and are potentially exposed to disruption of circadian rhythms
The International Classification of Sleep Disorders-2 (ICSD-2) defines shift work disorder (SWD) as insomnia and/or excessive sleepiness that associates with a prolonged shift work schedule which overlaps habitual sleeping time (AASM 2005)
The SWD and non-SWD groups were comparable in terms of sex, chronotype, shift work experience, frequency of physical exercise, alcohol consumption, smoking, and having successfully treated obstructive sleep apnoea (OSA)
Summary
In the European Union, 21% of the workforce do some form of shift work (Eurofound 2017) and are potentially exposed to disruption of circadian rhythms. Depending on the studied population, its shift schedules, and the instruments used to define the disorder, as much as 23–63% of shift workers have been reported as having SWD (Waage et al 2009; Rajaratnam et al 2011; Flo et al 2012; Di Milia et al 2013; Taniyama et al 2015) based on the International Classification of Sleep Disorders-2 (ICSD-2). The ICSD-2 defines SWD as insomnia and/or excessive sleepiness that associates with a prolonged shift work schedule which overlaps habitual sleeping time (AASM 2005). The revised edition, ICSD-3, (1) adds reduced total sleep time (TST) as an accompanying symptom, (2) increases the minimum manifestation time of the shift work schedule-associated symptoms from 1 to 3 months, and (3) increases the duration of sleep diary and actigraphy monitoring (whenever possible), demonstrating a disturbed sleep and wake pattern, from 1 to 2 weeks (AASM 2014)
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