Human phase response curve to intermittent blue light using a commercially available device

C. Eastman: Biological Rhythms Research Laboratory, 1645 W Jackson, Suite 425, Chicago, IL 60612, USA. .
The Journal of Physiology (Impact Factor: 5.04). 07/2012; 590(Pt 19):4859-68. DOI: 10.1113/jphysiol.2012.235416
Source: PubMed


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.

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Available from: Charmane Ina Eastman, Sep 25, 2014
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    • "The direction and magnitude of the shift is predicted by phase response curves (PRCs) [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]. Advancing the system (shifting it earlier) is more difficult and typically takes longer than delaying (shifting it later). "
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    Sleep Medicine 12/2014; 16(2). DOI:10.1016/j.sleep.2014.12.004 · 3.15 Impact Factor
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    • "In addition to time-dependence, several factors influence the magnitude of light-induced phase shifts including light duration , intensity, and color (Khalsa et al., 2003; Revell et al., 2012; St Hilaire et al., 2012; Rüger et al., 2013). In general, magnitude increases with increased duration and/or intensity, and full-spectrum " white " light works best; however, shortwavelength " blue " light (450–500 nm) has been shown to be nearly as effective as " white " light (Revell et al., 2012; Rüger et al., 2013). Bright light—when used in accordance with the principles of the known PRC to light—is highly effective at synchronizing circadian rhythms of physiology and behavior. "
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    Frontiers in Aging Neuroscience 12/2014; 6:325. DOI:10.3389/fnagi.2014.00325 · 4.00 Impact Factor
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    • "Although the shapes of PRCs are qualitatively similar in mammals, they differ quantitatively. This is attributed to variations in the intensity, duration and spectral composition of the light stimuli used (Comas et al., 2006; Revell et al., 2012; Sharma, 2003a; St Hilaire et al., 2012), as well as age of the organisms (Weinert, 1998). In addition, photic PRCs are characterized by the presence of light insensitive region (dead zones) during the subjective day (Johnson, 1999). "
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    ABSTRACT: Photic phase response curves (PRCs) have been extensively studied in many laboratory-bred diurnal and nocturnal rodents. However, comparatively fewer studies have addressed the effects of photic cues on wild diurnal mammals. Hence, we studied the effects of short durations of light pulses on the circadian systems of the diurnal Indian Palm squirrel, Funambulus pennanti. Adult males entrained to a light-dark cycle (12 h-12 h) were transferred to constant darkness (DD). Free-running animals were exposed to brief light pulses (250 lux) of 15 min, 3 circadian hours (CT) apart (CT 0, 3, 6, 9, 12, 15, 18 and 21). Phase shifts evoked at different phases were plotted against CT and a PRC was constructed. F. pennanti exhibited phase-dependent phase shifts at all the CTs studied, and the PRC obtained was of type 1 at the intensity of light used. Phase advances were evoked during the early subjective day and late subjective night, while phase delays occurred during the late subjective day and early subjective night, with maximum phase delay at CT 15 (-2.04 ± 0.23 h), and maximum phase advance at CT 21 (1.88 ± 0.31 h). No dead zone was seen at this resolution. The free-running period of the rhythm was concurrently lengthened (deceleration) during the late subjective day and early subjective night, while period shortening (acceleration) occurred during the late subjective night. The maximum deceleration was noticed at CT 15 (-0.40 ± 0.09 h) and the maximum acceleration at CT 21 (0.39 ± 0.07 h). A significant positive correlation exists between the phase shifts and the period changes (r = 0.684, p = 0.001). The shapes of both the PRC and period response curve (τRC) qualitatively resemble each other. This suggests that the palm squirrel's circadian system is entrained both by phase and period responses to light. Thus, F. pennanti exhibits robust clock-resetting in response to light pulses.
    Chronobiology International 11/2013; 31(3). DOI:10.3109/07420528.2013.851084 · 3.34 Impact Factor
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