Light-Induced Melatonin Suppression in Humans With Polychromatic and Monochromatic Light Chronobiology International, Nov 2007; 24(6): 1125–1137
Revell VL and Skene DJ.

"This pilot experiment investigated the hypothesis that only melanopsin drives [non-image forming] NIF responses in humans. The ability of polychromatic white light and monochromatic blue light (max 479 nm) matched for melanopsin stimulating photons to suppress nocturnal melatonin production was compared...a comparison of the two light conditions revealed a significantly enhanced response to polychromatic light"

"In conclusion, the current study has demonstrated the melatonin suppression response to polychromatic [white] light is enhanced compared to monochromatic [blue 479 nm] light matched in terms of melanopsin stimulation. This suggests that the response to polychromatic light cannot be predicted from the melanopsin photosensory spectral sensitivity and that it is not solely melanopsin that drives the melatonin suppression response..." Abstract

OUR NOTE: While the unadjusted irradiance {light intensity} from the polychromatic [i.e. white] light source used in this study is, by photon count or energy, between 2 to 3 times that of the blue light, the white light was more effective at suppressing melatonin than the monochromatic blue (479 nm) light. In comparison, the Lo-LIGHT has been found to be as effective as white light with over 10 times as much irradiance {light intensity}.

Phase Delaying the Human Circadian Clock with Blue-Enriched Polychromatic Light. Chronobiology International, May 2009; 26(4):709–725
Smith MR and Eastman CI.

"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. ...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" Abstract

Phase Delay shifts to Blue-Enriched VS. Standard Polychromatic White Light in Healthy Older people in a Semi-Ambulatory Setting. Sleep 2008. Vol 31, Abstract Supplement #0134:
Scheuemaier KD, Munch M, Guzik A, Silva EJ, Ronda JM, Duffy JM.

"The present study compared the phase delay shift produced by two different fluorescent lamp, standard poly chromatic vs. blue-enriched polychromatic white light."
"We studied 10 subjects ( mean age 63.3). ...Mean illuminance in the blue-enriched and standard white light groups was 1.07 x 10¹⁵ photons/cm²/sec and 1.025 x 10¹⁵ photons/cm²/sec respectively."
"Conclusion: At the same illuminance levels both light sources produced phase delays of similar magnitude."

Our NOTE: This study found that increasing the proportion of blue light wavelengths of a white light source does not improve the phase-shifting capability of a light source in older people as compared with a normal white light source. As in the two studies with younger subjects cited above this one, this study fails to demonstrate any increased efficiency (i.e. effectiveness at a lower light intensity or energy) from the use of enhanced levels of blue light wavelengths in light therapy lamps.

Phase Advancing the Human Circadian Clock with Blue-Enriched Polychromatic Light. Sleep Medicine (2009); 10(3):287–294
Smith MR, Revell VL, and Eastman CI.

"Lamps and light-producing devices emitting exclusively or relatively more short-wavelength energy are now commercially available. This provides clinicians and patient/consumers with a variety of choices when selecting a device for light treatment, but there remains little evidence from well controlled studies demonstrating the efficacy of those devices for circadian phase shifting.
The goal of the current study was to determine whether bright blue-enriched light could phase advance the circadian clock more than standard bright white light at light levels that are currently being used for therapeutic applications, and using light boxes designed for practical applications."

"Conclusion: Bright blue-enriched polychromatic light is no more effective than standard bright light therapy for phase advancing circadian rhythms at commonly used therapeutic light levels." Full Paper

NOTE: It has been well established for several years that increasing the proportion of blue light does NOT improve the effect of light therapy lamps. The following studies by leading researchers demonstrating that there is no basis for the continuing misinformation that blue light wavelengths are particularly effective for regulating human circadian rhythms or influencing human metabolic activitry are over a decade old. There are more recent studies that address this more directly. MORE

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