Phase Delaying the Human Circadian Clock with Blue-Enriched Polychromatic Light

Rush University Medical Center, Chicago, Illinois 60612, USA.
Chronobiology International (Impact Factor: 3.34). 06/2009; 26(4):709-25. DOI: 10.1080/07420520902927742
Source: PubMed


The human circadian system is maximally sensitive to short-wavelength (blue) light. In a previous study we found no difference between the magnitude of phase advances produced by bright white versus bright blue-enriched light using light boxes in a practical protocol that could be used in the real world. Since the spectral sensitivity of the circadian system may vary with a circadian rhythm, we tested whether the results of our recent phase-advancing study hold true for phase delays. In a within-subjects counterbalanced design, this study tested whether bright blue-enriched polychromatic light (17000 K, 4000 lux) could produce larger phase delays than bright white light (4100 K, 5000 lux) of equal photon density (4.2x10(15) photons/cm(2)/sec). Healthy young subjects (n = 13) received a 2 h phase delaying light pulse before bedtime combined with a gradually delaying sleep/dark schedule on each of 4 consecutive treatment days. On the first treatment day the light pulse began 3 h after the dim light melatonin onset (DLMO). An 8 h sleep episode began at the end of the light pulse. Light treatment and the sleep schedule were delayed 2 h on each subsequent treatment day. A circadian phase assessment was conducted before and after the series of light treatment days to determine the time of the DLMO and DLMOff. Phase delays in the blue-enriched and white conditions were not significantly different (DLMO: -4.45+/-2.02 versus -4.48+/-1.97 h; DLMOff: -3.90+/-1.97 versus -4.35+/-2.39 h, respectively). These results indicate that at light levels commonly used for circadian phase shifting, blue-enriched polychromatic light is no more effective than the white polychromatic lamps of a lower correlated color temperature (CCT) for phase delaying the circadian clock.

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Available from: Charmane Ina Eastman, Oct 13, 2015
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    • "Although studies have shown that short-wavelength light or “blue-enriched” light sources can be effective at correcting circadian sleep disorders,24,25 other studies failed to show differences between lamps of different correlated color temperatures (CCTs). Smith and Eastman26 compared the effectiveness of a 17,000 K lamp and a 4,100 K lamp in phase shifting the human circadian clock, under controlled laboratory conditions. The researchers did not find any significant differences between the light sources, most likely because they were using light levels above the saturation response of the circadian system. "
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    ABSTRACT: Background: Light therapy has shown great promise as a nonpharmacological method to improve symptoms associated with Alzheimer's disease and related dementias (ADRD), with preliminary studies demonstrating that appropriately timed light exposure can improve nighttime sleep efficiency, reduce nocturnal wandering, and alleviate evening agitation. Since the human circadian system is maximally sensitive to short-wavelength (blue) light, lower, more targeted lighting interventions for therapeutic purposes, can be used. Methods: The present study investigated the effectiveness of a tailored lighting intervention for individuals with ADRD living in nursing homes. Low-level "bluish-white" lighting designed to deliver high circadian stimulation during the daytime was installed in 14 nursing home resident rooms for a period of 4 weeks. Light-dark and rest-activity patterns were collected using a Daysimeter. Sleep time and sleep efficiency measures were obtained using the rest-activity data. Measures of sleep quality, depression, and agitation were collected using standardized questionnaires, at baseline, at the end of the 4-week lighting intervention, and 4 weeks after the lighting intervention was removed. Results: The lighting intervention significantly (P<0.05) decreased global sleep scores from the Pittsburgh Sleep Quality Index, and increased total sleep time and sleep efficiency. The lighting intervention also increased phasor magnitude, a measure of the 24-hour resonance between light-dark and rest-activity patterns, suggesting an increase in circadian entrainment. The lighting intervention significantly (P<0.05) reduced depression scores from the Cornell Scale for Depression in Dementia and agitation scores from the Cohen-Mansfield Agitation Inventory. Conclusion: A lighting intervention, tailored to increase daytime circadian stimulation, can be used to increase sleep quality and improve behavior in patients with ADRD. The present field study, while promising for application, should be replicated using a larger sample size and perhaps using longer treatment duration.
    Clinical Interventions in Aging 09/2014; 9:1527-37. DOI:10.2147/CIA.S68557 · 2.08 Impact Factor
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    • "During the relaxation block, subjects were asked to open their eyes and sit comfortably without performing any task. At the end of each light condition, the participants reported their subjective feelings on valence and arousal using a 11-point Likert scale.15) The endpoints for the valence scale were anchored at very unhappy and very happy, whereas the endpoints for the arousal scale were anchored at agitated and relaxed. "
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    ABSTRACT: It has been reported that working and learning efficiency might be increased through artificially controlling the color temperature and brightness of light. However, the neurological bases of these outcomes are not well established. Our study was designed to observe whether electroencephalogram (EEG) alpha frequency, as a candidate biological marker, demonstrates significant changes in response to alterations of specific light parameters. Thirty-two healthy subjects performed cognitive tasks under four different polychromatic light conditions: a combination of two different levels of color temperature (2766K vs. 5918K) and brightness (300 lux vs. 600 lux). Spectrum analyses were performed on alpha frequency. Subjects reported that they felt more pleasant in bright conditions and more relaxed in warm color temperature conditions. Our findings indicate that alpha power increases in warm, low-light and cool, high-light conditions, and there is a significant interaction between color temperature and brightness. EEGs might serve as a useful biological marker for further research related to the effects of polychromatic light on cognitive function.
    Clinical Psychopharmacology and Neuroscience 12/2013; 11(3):126-31. DOI:10.9758/cpn.2013.11.3.126
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    • "The identification of melanopsin led lighting manufacturers to develop 'blue light' products or 'blue-enriched' white lights. At the high intensities typically used in light treatment paradigms the blue-enriched lights perform similarly to white light, presumably because the system is saturated (Smith & Eastman, 2009; Smith et al. 2009; Terman, 2009). However, if melanopsin is being specifically targeted then it should be possible to reduce the irradiance and duration of the light whilst still inducing an effect. "
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    ABSTRACT: Key points  Misalignment between the internal circadian clock driving daily rhythms in physiology and behaviour, such as sleepiness, performance and metabolism, and the sleep-wake schedule, as occurs in jet lag and night shift work, can have profound, harmful consequences for health, performance and safety.  Light applied at specific times of day can be used to shift the timing of the clock and reduce this circadian misalignment.  We show for the first time that a small, commercially available, portable blue light device is capable of shifting the clock when it is administered daily over a 2 h window (90 min blue light as 30 min pulses with 15 min breaks).  The direction and amount that the clock is shifted depends on the time of day that the light is administered.  The results of this work provide a practical, effective light treatment that can be used in the real world.
    The Journal of Physiology 07/2012; 590(Pt 19):4859-68. DOI:10.1113/jphysiol.2012.235416 · 5.04 Impact Factor
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