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Blue-enriched versus white light for circadian phase delays.

Smith-MR; Lee-C; Revell-VL; Eastman-CI
Proceedings of the 10th meeting of the Society for Research on Biological Rhythms, May 21-25, 2006, Sandestin, Florida. Urbana, IL: Society for Research on Biological Rhythms, 2006 May; :131
The human circadian system is most sensitive to short wavelength (blue) light. We previously found that bright blue-enriched light produced larger phase advances than bright white light, when sleep/dark was advanced. This study compared the magnitude of phase delays induced by bright blue-enriched light and bright white light, when sleep/dark was delayed. Five 15-minute intermittent light pulses interspersed by 45 minutes of normal room light were delivered on each of two consecutive nights, from 00:45 to 05:00, to coincide with the delay portion of the PRC. Subjects received either blue-enriched light (17,000K, n=10) or white light, (5,095K, n=12). Subjects were exposed to similar luminance from the blue-enriched and white lamps (~3900 vs ~3500 lux), but more total photons (4.6 vs 2.9 x 1015 photons/cm2/sec), and nearly 3 times as many photons in the blue (400-490nm) range (2.0 x 1015 vs 7.4 x 1014 photons/cm2/sec) from the blue-enriched lamps. The dim light melatonin onset (DLMO) and offset (DLMOff) were assessed before and after the light pulses. Mean (+/- SD) phase delays for the white and blue groups were 3.2 +/- 1.3 and 3.2 +/- 1.4 hours for the DLMO, and 3.6 +/- 1.6 and 1.4 +/- 1.5 hours for the DLMOff. Thus, the blueenriched and white light delayed the DLMO a similar amount, while the white light delayed the DLMOff significantly more. These surprising results will be discussed in terms of putative morning and evening oscillators.
Circadian-rhythms; Light-source; Light-waves; Lighting; Lighting-systems; Sleep-disorders
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Proceedings of the 10th meeting of the Society for Research on Biological Rhythms, May 21-25, 2006
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Rush University Medical Center, Chicago, Illinois