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Charmane I. Eastman - One of the best experts on this subject based on the ideXlab platform.
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bright light dark and melatonin can promote circadian adaptation in night shift workers
Sleep Medicine Reviews, 2002Co-Authors: Helen J Burgess, Katherine M Sharkey, Charmane I. EastmanAbstract:Abstract The circadian rhythms of shift workers do not usually phase shift to adapt to working at night and sleeping during the day. This misalignment results in a multitude of negative symptoms including poor performance and reduced alertness during night work and poor daytime sleep at home. After an introduction to circadian principles, we discuss the efficacy of appropriately timed bright light exposure (natural and artificial) and exogenous melatonin administration for producing circadian adaptation to night work. Interventions that generate alternative 24h light/dark patterns that facilitate appropriate circadian phase shifting are discussed. Such interventions include minimizing night workers' exposure to the external light/dark cycle, and the use of intermittent and moving patterns of bright light at work. The efficacy of melatonin in phase shifting circadian rhythms in the field is also addressed and compared to that of bright light. We present sleep/light exposure schedules that could produce circadian adaptation in permanent night workers. We conclude this review by discussing the impact of individual differences on possible circadian interventions and issues associated with the use of bright light interventions in the field.
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how to use light and dark to produce circadian adaptation to night shift work
Annals of Medicine, 1999Co-Authors: Charmane I. Eastman, Stacia K MartinAbstract:The circadian rhythms of night shift workers do not usually adjust to their unusual work and sleep schedules, reducing their quality of life and producing potentially dangerous health and safety problems. This paper reviews field studies of simulated night work in which shifted light-dark cycles were constructed with artificial bright or medium-intensity light to produce circadian adaptation, ie the shifting of circadian rhythms to align with night work and day sleep schedules. By using these studies we describe fundamental principles of human circadian rhythms relevant to producing circadian adaptation to night shift work at a level designed for the reader with only a basic knowledge of circadian rhythms. These principles should enable the reader to start designing work/sleep-light/dark schedules for producing circadian adaptation in night shift workers. One specific schedule is presented as an example. Finally, we discuss phase-response curves to light and clarify common misconceptions about the product...
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light treatment for sleep disorders consensus report vii jet lag
Journal of Biological Rhythms, 1995Co-Authors: Ziad Boulos, Derk-jan Dijk, Scott S Campbell, Alfred J Lewy, Michael Terman, Charmane I. EastmanAbstract:Sleep disturbances are an all-too-familiar symptom of jet lag and a prime source of complaints for transmeridian travelers and flight crews alike. They are the result of a temporary loss of synchrony between an abruptly shifted sleep period, timed in accordance with the new local day-night cycle, and a gradually reentraining circadian system. Scheduled exposure to bright light can, in principle, alleviate the symptoms of jet lag by accelerating circadian reentrainment to new time zones. Laboratory simulations, in which sleep time is advanced by 6 to 8 h and the subjects exposed to bright light for 3 to 4 h during late subjective night on 2 to 4 successive days, have not all been successful. The few field studies conducted to date have had encouraging results, but their applicability to the population at large remains uncertain due to very limited sample sizes. Unresolved issues include optimal times for light exposure on the first as well as on subsequent treatment days, whether a given, fixed, light exposure time is likely to benefit a majority of travelers or whether light treatment should be scheduled instead according to some individual circadian phase marker, and if so, can such a phase marker be found that is both practical and reliable.
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light treatment for sleep disorders consensus report vi shift work
Journal of Biological Rhythms, 1995Co-Authors: Charmane I. Eastman, Derk-jan Dijk, Ziad Boulos, Scott S Campbell, Michael Terman, Alfred J LewyAbstract:The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light...
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dark goggles and bright light improve circadian rhythm adaptation to night shift work
Sleep, 1994Co-Authors: Charmane I. Eastman, Karen T Stewart, Michael P Mahoney, Louis FoggAbstract:: We compared the contributions of bright light during the night shift and dark goggles during daylight for phase shifting the circadian rhythm of temperature to realign with a 12-hour shift of sleep. After 10 baseline days there were 8 night-work/day-sleep days. Temperature was continuously recorded from 50 subjects. There were four groups in a 2 x 2 design: light (bright, dim), goggles (yes, no). Subjects were exposed to bright light (about 5,000 lux) for 6 hours on the first 2 night shifts. Dim light was < 500 lux. Both bright light and goggles were significant factors for producing circadian rhythm phase shifts. The combination of bright light plus goggles was the most effective, whereas the combination of dim light and no goggles was the least effective. The temperature rhythm either phase advanced or phase delayed when it aligned with daytime sleep. However, when subjects did not have goggles only phase advances occurred. Goggles were necessary for producing phase delays. The most likely explanation is that daylight during the travel-home window after a night shift inhibits phase-delay shifts, and goggles can prevent this inhibition. Larger temperature-rhythm phase shifts were associated with better subjective daytime sleep, less subjective fatigue and better mood.
Derk-jan Dijk - One of the best experts on this subject based on the ideXlab platform.
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daytime exposure to bright light as compared to dim light decreases sleepiness and improves psychomotor vigilance performance
Sleep, 2003Co-Authors: Jo Phippsnelson, Jennifer R. Redman, Derk-jan Dijk, Shanthakumar M W RajaratnamAbstract:STUDY OBJECTIVES: This study examined the effects of bright light exposure, as compared to dim light, on daytime subjective sleepiness, incidences of slow eye movements (SEMs), and psychomotor vigilance task (PVT) performance following 2 nights of sleep restriction. DESIGN: The study had a mixed factorial design with 2 independent variables: light condition (bright light, 1,000 lux; dim light, < 5 lux) and time of day. The dependent variables were subjective sleepiness, PVT performance, incidences of SEMs, and salivary melatonin levels. SETTING: Sleep research laboratory at Monash University. PARTICIPANTS: Sixteen healthy adults (10 women and 6 men) aged 18 to 35 years (mean age 25 years, 3 months). INTERVENTIONS: Following 2 nights of sleep restriction (5 hours each night), participants were exposed to modified constant routine conditions. Eight participants were exposed to bright light from noon until 5:00 pm. Outside the bright light exposure period (9:00 am to noon, 5:00 pm to 9:00 pm) light levels were maintained at less than 5 lux. A second group of 8 participants served as controls for the bright light exposure and were exposed to dim light throughout the entire protocol. MEASUREMENTS AND RESULTS: Bright light exposure reduced subjective sleepiness, decreased SEMs, and improved PVT performance compared to dim light. Bright lights had no effect on salivary melatonin. A significant positive correlation between PVT reaction times and subjective sleepiness was observed for both groups. Changes in SEMs did not correlate significantly with either subjective sleepiness or PVT performance. CONCLUSIONS: Daytime bright light exposure can reduce the impact of sleep loss on sleepiness levels and performance, as compared to dim light. These effects appear to be mediated by mechanisms that are separate from melatonin suppression. The results may assist in the development of treatments for daytime sleepiness. Language: en
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light treatment for sleep disorders consensus report vii jet lag
Journal of Biological Rhythms, 1995Co-Authors: Ziad Boulos, Derk-jan Dijk, Scott S Campbell, Alfred J Lewy, Michael Terman, Charmane I. EastmanAbstract:Sleep disturbances are an all-too-familiar symptom of jet lag and a prime source of complaints for transmeridian travelers and flight crews alike. They are the result of a temporary loss of synchrony between an abruptly shifted sleep period, timed in accordance with the new local day-night cycle, and a gradually reentraining circadian system. Scheduled exposure to bright light can, in principle, alleviate the symptoms of jet lag by accelerating circadian reentrainment to new time zones. Laboratory simulations, in which sleep time is advanced by 6 to 8 h and the subjects exposed to bright light for 3 to 4 h during late subjective night on 2 to 4 successive days, have not all been successful. The few field studies conducted to date have had encouraging results, but their applicability to the population at large remains uncertain due to very limited sample sizes. Unresolved issues include optimal times for light exposure on the first as well as on subsequent treatment days, whether a given, fixed, light exposure time is likely to benefit a majority of travelers or whether light treatment should be scheduled instead according to some individual circadian phase marker, and if so, can such a phase marker be found that is both practical and reliable.
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light treatment for sleep disorders consensus report vi shift work
Journal of Biological Rhythms, 1995Co-Authors: Charmane I. Eastman, Derk-jan Dijk, Ziad Boulos, Scott S Campbell, Michael Terman, Alfred J LewyAbstract:The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light...
Alfred J Lewy - One of the best experts on this subject based on the ideXlab platform.
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light treatment for sleep disorders consensus report vii jet lag
Journal of Biological Rhythms, 1995Co-Authors: Ziad Boulos, Derk-jan Dijk, Scott S Campbell, Alfred J Lewy, Michael Terman, Charmane I. EastmanAbstract:Sleep disturbances are an all-too-familiar symptom of jet lag and a prime source of complaints for transmeridian travelers and flight crews alike. They are the result of a temporary loss of synchrony between an abruptly shifted sleep period, timed in accordance with the new local day-night cycle, and a gradually reentraining circadian system. Scheduled exposure to bright light can, in principle, alleviate the symptoms of jet lag by accelerating circadian reentrainment to new time zones. Laboratory simulations, in which sleep time is advanced by 6 to 8 h and the subjects exposed to bright light for 3 to 4 h during late subjective night on 2 to 4 successive days, have not all been successful. The few field studies conducted to date have had encouraging results, but their applicability to the population at large remains uncertain due to very limited sample sizes. Unresolved issues include optimal times for light exposure on the first as well as on subsequent treatment days, whether a given, fixed, light exposure time is likely to benefit a majority of travelers or whether light treatment should be scheduled instead according to some individual circadian phase marker, and if so, can such a phase marker be found that is both practical and reliable.
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light treatment for sleep disorders consensus report vi shift work
Journal of Biological Rhythms, 1995Co-Authors: Charmane I. Eastman, Derk-jan Dijk, Ziad Boulos, Scott S Campbell, Michael Terman, Alfred J LewyAbstract:The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light...
Charles A Czeisler - One of the best experts on this subject based on the ideXlab platform.
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efficacy of intermittent exposure to bright light for treating maladaptation to night work on a counterclockwise shift work rotation
Scandinavian Journal of Work Environment & Health, 2021Co-Authors: Heidi Lammersvan Der M Holst, Jeanne F Duffy, Joseph M Ronda, Todd S Horowitz, James K Wyatt, John Wise, Wei Wang, Charles A CzeislerAbstract:Objectives Rotating shift work is associated with adverse outcomes due to circadian misalignment, sleep curtailment, work-family conflicts, and other factors. We tested a bright light countermeasure to enhance circadian adaptation on a counterclockwise rotation schedule. Methods Twenty-nine adults (aged 20–40 years; 15 women) participated in a 4-week laboratory simulation with weekly counterclockwise transitions from day, to night, to evening, to day shifts. Each week consisted of five 8-hour workdays including psychomotor vigilance tests, two days off, designated 8-hour sleep episodes every day, and an assessment of circadian melatonin secretion. Participants were randomized to a treatment group (N=14), receiving intermittent bright light during work designed to facilitate circadian adaptation, or a control group (N=15) working in indoor light. Adaptation was measured by how much of the melatonin secretion episode overlapped with scheduled sleep timing. Results On the last night shift, there was a greater overlap between melatonin secretion and scheduled sleep time in the treatment group [mean 4.90, standard deviation (SD) 2.8 hours] compared to the control group (2.62, SD 2.8 hours; P=0.002), with night shift adaptation strongly influenced by baseline melatonin timing (r 2 =-0.71, P=0.01). While the control group exhibited cognitive deficits on the last night shift, the treatment group’s cognitive deficits on the last night and evening shifts were minimized. Conclusions In this laboratory setting, intermittent bright light during work hours enhanced adaptation to night work and subsequent readaptation to evening and day work. Light regimens scheduled to shift circadian timing should be tested in actual shift workers on counterclockwise schedules as a workplace intervention.
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circadian phase resetting by a single short duration light exposure
JCI insight, 2017Co-Authors: Shadab A Rahman, Charles A Czeisler, Jeanne F Duffy, Richard E Kronauer, Melissa A St Hilaire, Annemarie Chang, Nayantara Santhi, Steven W Lockley, Elizabeth B KlermanAbstract:BACKGROUND. In humans, a single light exposure of 12 minutes and multiple-millisecond light exposures can shift the phase of the circadian pacemaker. We investigated the response of the human circadian pacemaker to a single 15-second or 2-minute light pulse administered during the biological night. METHODS. Twenty-six healthy individuals participated in a 9-day inpatient protocol that included assessment of dim light melatonin onset time (DLMO time) before and after exposure to a single 15-second (n = 8) or 2-minute (n = 12) pulse of bright light (9,500 lux; 4,100 K fluorescent) or control background dim light (<3 lux; n = 6). Phase shifts were calculated as the difference in clock time between the two phase estimates. RESULTS. Both 15-second and 2-minute exposures induced phase delay shifts [median (± SD)] of –34.8 ± 47.2 minutes and –45.4 ± 28.4 minutes, respectively, that were significantly (P = 0.04) greater than the control condition (advance shift: +22.3 ± 51.3 minutes) but were not significantly different from each other. Comparisons with historic data collected under the same conditions confirmed a nonlinear relationship between exposure duration and the magnitude of phase shift. CONCLUSIONS. Our results underscore the exquisite sensitivity of the human pacemaker to even short-duration single exposures to light. These findings may have real-world implications for circadian disruption induced by exposure to brief light stimuli at night.
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efficacy of bright light and sleep darkness scheduling in alleviating circadian maladaptation to night work
American Journal of Physiology-endocrinology and Metabolism, 2001Co-Authors: Todd S Horowitz, Brian E Cade, Jeremy M Wolfe, Charles A CzeislerAbstract:We tested the hypothesis that circadian adaptation to night work is best achieved by combining bright light during the night shift and scheduled sleep in darkness. Fifty-four subjects participated in a shift work simulation of 4 day and 3 night shifts followed by a 38-h constant routine (CR). Subjects received 2,500 lux (Bright Light) or 150 lux (Room Light) during night shifts and were scheduled to sleep (at home in darkened bedrooms) from 0800 to 1600 (Fixed Sleep) or ad libitum (Free Sleep). Dim light melatonin onset (DLMO) was measured before and after the night shifts. Both Fixed Sleep and Bright Light conditions significantly phase delayed DLMO. Treatments combined additively, with light leading to larger phase shifts. Free Sleep subjects who spontaneously adopted consistent sleep schedules adapted better than those who did not. Neither properly timed bright light nor fixed sleep schedules were consistently sufficient to shift the melatonin rhythm completely into the sleep episode. Scheduling of sleep/darkness should play a major role in prescriptions for overcoming shift work-related phase misalignment.
Ziad Boulos - One of the best experts on this subject based on the ideXlab platform.
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light treatment for sleep disorders consensus report vii jet lag
Journal of Biological Rhythms, 1995Co-Authors: Ziad Boulos, Derk-jan Dijk, Scott S Campbell, Alfred J Lewy, Michael Terman, Charmane I. EastmanAbstract:Sleep disturbances are an all-too-familiar symptom of jet lag and a prime source of complaints for transmeridian travelers and flight crews alike. They are the result of a temporary loss of synchrony between an abruptly shifted sleep period, timed in accordance with the new local day-night cycle, and a gradually reentraining circadian system. Scheduled exposure to bright light can, in principle, alleviate the symptoms of jet lag by accelerating circadian reentrainment to new time zones. Laboratory simulations, in which sleep time is advanced by 6 to 8 h and the subjects exposed to bright light for 3 to 4 h during late subjective night on 2 to 4 successive days, have not all been successful. The few field studies conducted to date have had encouraging results, but their applicability to the population at large remains uncertain due to very limited sample sizes. Unresolved issues include optimal times for light exposure on the first as well as on subsequent treatment days, whether a given, fixed, light exposure time is likely to benefit a majority of travelers or whether light treatment should be scheduled instead according to some individual circadian phase marker, and if so, can such a phase marker be found that is both practical and reliable.
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light treatment for sleep disorders consensus report vi shift work
Journal of Biological Rhythms, 1995Co-Authors: Charmane I. Eastman, Derk-jan Dijk, Ziad Boulos, Scott S Campbell, Michael Terman, Alfred J LewyAbstract:The unhealthy symptoms and many deleterious consequences of shift work can be explained by a mismatch between the work-sleep schedule and the internal circadian rhythms. This mismatch occurs because the 24-h zeitgebers, such as the natural light-dark cycle, keep the circadian rhythms from phase shifting to align with the night-work, day-sleep schedule. This is a review of studies in which the sleep schedule is shifted several hours, as in shift work, and bright light is used to try to phase shift circadian rhythms. Phase shifts can be produced in laboratory studies, when subjects are kept indoors, and faster phase shifting occurs with appropriately timed bright light than with ordinary indoor (dim) light. Bright light field studies, in which subjects live at home, show that the use of artificial nocturnal bright light combined with enforced daytime dark (sleep) periods can phase shift circadian rhythms despite exposure to the conflicting 24-h zeitgebers. So far, the only studies on the use of bright light...