Differences in Sleep, Light, and Circadian Phase in Offshore 18:00–06:00 h and 19:00–07:00 h Shift Workers

Thorne, Helen C.; Hampton, Shelagh M.; Morgan, Linda; Skene, Debra J.; Arendt, Joséphine

doi:10.1080/07420520802106850

Cited by 40 publications

(26 citation statements)

References 36 publications

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“…The response to different shift schedules in the North Sea varies, with fewer people fully adapting to a 19:00–07:00 h night shift compared to a 18:00–06:00 h shift (Thorne et al, 2008), and with seasonal differences in response that have been attributed to different photoperiods in different seasons (Barnes et al, 1998b). The most time spent desynchronized was during a swing shift of 1 wk of 18:00–06:00 h followed by 1 wk of 06:00–18:00 h (Gibbs et al, 2004; see also for pdf file).…”

Section: Polar Studiesmentioning

confidence: 99%

Biological Rhythms During Residence in Polar Regions

Arendt¹

2012

Chronobiology International

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128

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At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 × 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with “normal” working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75°S, base personnel adapt the circadian system to night work within a week, in contrast to temperate zones where complete adaptation rarely occurs. A similar situation occurs on high-latitude North Sea oil installations, especially when working 18:00–06:00 h. Lack of conflicting light exposure (and “social obligations”) is the probable explanation. Many have problems returning to day work, showing circadian desynchrony. Timed light treatment again has helped to restore normal phase/sleep in a small number of people. Postprandial response to meals is compromised during periods of desynchrony with evidence of insulin resistance and elevated triglycerides, risk factors for heart disease. Only small numbers of subjects have been studied intensively in polar regions; however, these observations suggest that suboptimal light conditions are deleterious to health. They apply equally to people living in temperate zones with insufficient light exposure.

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Section: Polar Studiesmentioning

confidence: 99%

Biological Rhythms During Residence in Polar Regions

Arendt¹

2012

Chronobiology International

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128

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“…One solution to the shift‐work problems is often sought in helping the biological clock of shift workers entrain to the different shifts, predominantly to the night shift but also to the morning shifts, when workers have to get up as early as 4 am to get to work on time. Bright light (>1000 lx) has been shown to facilitate re‐entrainment of the biological clock of subjects in shift‐work simulations 25,75,76 and of shift workers in field studies (Miriam Havel, Jan Rémi and Till Roenneberg, unpublished data, 2010) 143,144 . One has to keep in mind though, that the efficacy of light as zeitgeber depends on many aspects: duration, wavelength, applied protocol (continuous vs intermittent), the individual circadian phase at which a worker is exposed to the light, and on his or her “light history.” 145 The ability of light at night to suppress melatonin, for example, correlates negatively with prior daytime light exposure 145,146 .…”

Section: Where Should We Go?mentioning

confidence: 99%

Shift-work research: Where do we stand, where should we go?

Kantermann

Juda

Vetter

et al. 2010

Sleep and Biological Rhythms

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Shift-work seriously affects the health and well-being of millions of people worldwide, and the number of shift workers is constantly rising (currently approximately 20% of the workforce). While some effects are acute, others lead to chronic syndromes that persist after retirement. Though health problems in shift workers are well established, we still do not properly understand the causal mechanisms underlying shift-work's effects on health. One reason may be the heterogeneity in shift-work research design and methodology, rendering comparison between studies difficult or even impossible. Shift-work also involves a multitude of interacting factors, and we do not yet fully understand many of these interactions. Interindividual differences between workers are central predictors for health. Among these, individual differences in internal time (chronotype) should play a key role in a worker's ability to adjust to shift-work. While the importance of chronotype is receiving increased attention in chronobiology, it is still being largely ignored by shift-work studies, particularly by those performed in the field. Shift-work research would greatly benefit from increased attention to circadian components in real-life shift-work situations.Here, we summarize the current state of shift-work research in an attempt to address the reasons as to why we still do not clearly understand the links between shift-work and health. The aim of shift-work research should ultimately be to improve health and well-being (including social issues) in shift workers by means of improved work schedules. Society as a whole would benefit from such improvements -the individual worker, the health system, and industry.

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“…If shift workers fully adapt to an offshore night shift they will be out of synchrony with their home environment upon returning home, with consequent problems of poor night sleep, reduced daytime alertness and performance and possible digestive problems. Factors such as season, 13 length and timing of the shift, 12,14 early or late initial circadian phase, 15 light exposure, 9 and sleep/wake patterns (as these indirectly affect light exposure), may all affect circadian adaptation. The use of light treatment at home, appropriately timed, may alleviate/reduce the physiological and behavioral problems caused by circadian rhythm disturbance experienced following offshore night‐shift work 5,16 …”

Section: Introductionmentioning

confidence: 99%

Returning from night shift to day life: Beneficial effects of light on sleep

Thorne¹,

Hampton²,

Morgan

et al. 2010

Sleep and Biological Rhythms

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Subjects working a 12 h offshore night shift for 2 weeks normally adapt to the night shift and are out of synchrony when they return home to day life, with consequent problems of poor sleep. The aim of this study was to investigate the effectiveness of timed light treatment to hasten circadian adaptation and improve sleep after the night shift. Ten male shift workers worked 19.00–07.00 h (n= 4) or 18.00–06.00 h (n= 6) offshore shift schedules. They were assessed for the last 7 days of a 14 or 21 day offshore night shift and for the following 14 days at home. Either timed light treatment/sunglasses or no light treatment/no sunglasses were scheduled in a crossover design during days 1–5 after the nightshift, theoretically timed to advance the circadian system. Subjects completed the Horne Östberg questionnaire. They wore an Actiwatch‐L throughout the study to monitor light/activity and completed daily sleep diaries. Actigraphic sleep efficiency after the light/sunglasses treatment was significantly improved (days 1–5), that is, 86.7 ± 5.8% (mean ± SD; light treatment) compared to 79.4 ± 10.3% (no light treatment), P < 0.05. Objective sleep duration (days 6–14) was significantly improved in the light treatment leg; actigraphic sleep duration was longer after light treatment (6.75 ± 0.50 h) compared to 5.76 ± 0.73 h, P < 0.05. If appropriately timed, light and darkness has beneficial effects on sleep efficiency and sleep duration following a night shift.

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Differences in Sleep, Light, and Circadian Phase in Offshore 18:00–06:00 h and 19:00–07:00 h Shift Workers

Cited by 40 publications

References 36 publications

Biological Rhythms During Residence in Polar Regions

Biological Rhythms During Residence in Polar Regions

Shift-work research: Where do we stand, where should we go?

Returning from night shift to day life: Beneficial effects of light on sleep

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