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Walbeek, T. J., Harrison, E. M., Soler, R. R., & Gorman, M. R. (2019). Enhanced Circadian Entrainment in Mice and Its Utility under Human Shiftwork Schedules. Clocks & Sleep, 1(3), 394–413.
Abstract: The circadian system is generally considered to be incapable of adjusting to rapid changes in sleep/work demands. In shiftworkers this leads to chronic circadian disruption and sleep loss, which together predict underperformance at work and negative health consequences. Two distinct experimental protocols have been proposed to increase circadian flexibility in rodents using dim light at night: rhythm bifurcation and T-cycle (i.e., day length) entrainment. Successful translation of such protocols to human shiftworkers could facilitate alignment of internal time with external demands. To assess entrainment flexibility following bifurcation and exposure to T-cycles, mice in Study 1 were repeatedly phase-shifted. Mice from experimental conditions rapidly phase-shifted their activity, while control mice showed expected transient misalignment. In Study 2 and 3, mice followed a several weeks-long intervention designed to model a modified DuPont or Continental shiftwork schedule, respectively. For both schedules, bifurcation and nocturnal dim lighting reduced circadian misalignment. Together, these studies demonstrate proof of concept that mammalian circadian systems can be rendered sufficiently flexible to adapt to multiple, rapidly changing shiftwork schedules. Flexible adaptation to exotic light-dark cycles likely relies on entrainment mechanisms that are distinct from traditional entrainment.
Keywords: Animals
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Savarese, M., & Di Perri, M. C. (2019). Excessive sleepiness in shift work disorder: a narrative review of the last 5 years. Sleep Breath, , 1–14.
Abstract: INTRODUCTION: Shift work sleep disorder (SWSD), also known as shift work disorder (SWD), is a circadian rhythm sleep disorder characterized by insomnia and/or excessive sleepiness, associated with a recurring work schedule that overlaps the usual time designated for sleeping. PURPOSE: This article aims to provide a narrative review of the pharmacological trials conducted on SWD in the last 5 years, to better address safety and health issues inherent to this disorder. METHODS: An electronic literature search was conducted using PubMed. All eligible randomized controlled trials (RCTs) and cross-over RCTs with employees undertaking shift work (including night shifts) were considered, yielding three articles. RESULTS: All three studies showed the efficacy of armodafinil in improving subjective and objective sleepiness, clinical conditions, and global functioning regardless of shift duration. Both performance and driving simulator performance tests administered during the night shift bore better results following armodafinil administration than after placebo. However, armodafinil only reduced subjective disability in individuals working more than 9 h; furthermore, even after armodafinil, alertness was reduced but not normalized. CONCLUSION: These studies underscore the importance of preventing and/or minimizing disturbances due to shift work. This may be achieved through various strategies, such as the employer's commitment to adopt ergonomic criteria in shift design and to implement work-environment interventions like controlled bright light. Health personnel is of pivotal importance to detect potential factors of intolerance to shift work or early symptoms of SWD. Additional and improved studies are needed to further evaluate the effectiveness and safety of both pharmacological and non-pharmacological interventions.
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Sletten, T. L., Cappuccio, F. P., Davidson, A. J., Van Cauter, E., Rajaratnam, S. M. W., & Scheer, F. A. J. L. (2020). Health consequences of circadian disruption. Sleep, 43(1).
Abstract: The circadian system is key for optimal functioning by maintaining synchrony between internal circadian rhythms, behaviors, and external cues. Many clinicians are not fully aware, however, of the far-reaching implications of the circadian system for human health. Clinical attention to circadian rhythms has largely focused on sleep disturbances. The impact of the circadian system on health is, however, much broader. Clinical diagnoses are often based on single time point assessments during the day, ignoring circadian influences on physiology. Even when time is considered, using (external) clock time ignores the large interindividual differences in internal timing.
Keywords: Human Health; Circadian Rhythm; Chronobiology; Sleep; Review
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Aarts, M. P. J., Hartmeyer, S. L., Morsink, K., Kort, H. S. M., & de Kort, Y. A. W. (2020). Can Special Light Glasses Reduce Sleepiness and Improve Sleep of Nightshift Workers? A Placebo-Controlled Explorative Field Study. Clocks & Sleep, 2(2), 225–245.
Abstract: Nightshift workers go against the natural sleep–wake rhythm. Light can shift the circadian clock but can also induce acute alertness. This placebo-controlled exploratory field study examined the effectiveness of light glasses to improve alertness while reducing the sleep complaints of hospital nurses working nightshifts. In a crossover within-subjects design, 23 nurses participated, using treatment glasses and placebo glasses. Sleepiness and sleep parameters were measured. A linear mixed model analysis on sleepiness revealed no significant main effect of the light intervention. An interaction effect was found indicating that under the placebo condition, sleepiness was significantly higher on the first nightshift than on the last night, while under the treatment condition, sleepiness remained stable across nightshift sessions. Sleepiness during the commute home also showed a significant interaction effect, demonstrating that after the first nightshift, driver sleepiness was higher for placebo than for treatment. Subjective sleep quality showed a negative main effect of treatment vs. placebo, particularly after the first nightshift. In retrospect, both types of light glasses were self-rated as effective. The use of light glasses during the nightshift may help to reduce driver sleepiness during the commute home, which is relevant, as all participants drove home by car or (motor) bike.
Keywords: Human Health
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Panagiotou, M., Rohling, J. H. T., & Deboer, T. (2020). Sleep Network Deterioration as a Function of Dim-Light-At-Night Exposure Duration in a Mouse Model. Clocks & Sleep, 2(3), 308–324.
Abstract: Artificial light, despite its widespread and valuable use, has been associated withdeterioration of health and well-being, including altered circadian timing and sleep disturbances,particularly in nocturnal exposure. Recent findings from our lab reveal significant sleep andsleep electroencephalogram (EEG) changes owing to three months exposure to dim-light-at-night(DLAN). Aiming to further explore the detrimental effects of DLAN exposure, in the present study,we continuously recorded sleep EEG and the electromyogram for baseline 24-h and following 6-h sleepdeprivation in a varied DLAN duration scheme. C57BL/6J mice were exposed to a 12:12 h light:DLANcycle (75lux:5lux) vs. a 12:12 h light:dark cycle (75lux:0lux) for one day, one week, and one month.Our results show that sleep was already affected by a mere day of DLAN exposure with additionalcomplications emerging with increasing DLAN exposure duration, such as the gradual delay ofthe daily 24-h vigilance state rhythms. We conducted detrended fluctuation analysis (DFA) on thelocomotor activity data following 1-month and 3-month DLAN exposure, and a significantly lesshealthy rest-activity pattern, based on the decreased alpha values, was found in both conditionscompared to the control light-dark. Taking into account the behavioral, sleep and the sleep EEGparameters, our data suggest that DLAN exposure, even in the shortest duration, induces deleteriouseffects; nevertheless, potential compensatory mechanisms render the organism partly adjustable andable to cope. We think that, for this reason, our data do not always depict linear divergence amonggroups, as compared with control conditions. Chronic DLAN exposure impacts the sleep regulatorysystem, but also brain integrity, diminishing its adaptability and reactivity, especially apparent in thesleep EEG alterations and particular low alpha values following DFA.
Keywords: Animals
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