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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    • "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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    • "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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