Blue Light is Not More Efficient than White Light for Light Therapy

A new study conducted at Harvard University and published in the May 12, 2010 issue of the journal Science Translational Medicine appears to confirm the conclusions of previous studies which found increasing the proportion of blue light wavelengths from a light therapy lamp has no benefit and does not improve effectiveness or efficiency. The authors of this study include many of the researchers whose earlier works are widely cited as validating the use of increased levels of blue wavelengths of light to improve the efficiency of light therapy. [GC Brainard, CA Ceisler, SW Lockley etc.] The editorial comment accompanying the article reflecting this change in understanding suggests "blue light now often used for therapy in depression or shift work should perhaps be replaced by green or white illumination."¹ [Science Translational Medicine is the American Association for the Advancement of Science journal directed toward the implementation of scientific research into the practice of medicine]

The study's authors state "Our results indicate that short-duration (<90 min) retinal exposure to narrow-bandwidth 555-nm [yellow-green]light..may be as effective, if not more effective, than an equivalent photon dose of 460-nm [blue] light."² Since treatment with light therapy generally takes less than 60 minutes, there would be no benefit in the use of blue light therapy or in increasing the proportion of blue light wavelengths in a light source used for light therapy. It is important to note that the subjects used in this study were under 30 years of age, as previous studies have shown there is a substantial decrease in the efficacy of blue light therapy in people over 40 years old. This is considered to be a consequence of the age-related yellowing of the lens which increasingly and significantly limits the amount of blue light that reaches the retina after age 40.

In assesing the relevance of this study of the efficacy of blue light (460 nm) on light therapy, the authors state "Our findings have implications for the development and optimization of light therapies for a number of disorders, including circadian rhythm sleep disorders, seasonal affective disorder (SAD), and dementia, and the use of light as an alerting stimulus to counter the sleepiness associated with misalignment of circadian phase, particularly during night shift work". In contrast to these finding regarding a lack of efficacy of blue light wavelengths, a number of studies on the use of light in the treatment of depression, and as well as studies on the use of light for regulating circadian phase and on light induced melatonin suppression published in major peer-reviewed journals have demonstrated that light from a Sunnex Biotechnologies Lo-LIGHT therapy lamp is as effective as "bright" white light therapy that provides more than 10 times the intensity or brightness. Additionally, as discussed elsewhere on this web site, the low intensity GreenLIGHT technology used in the Lo-LIGHT therapy lamps poses no risk to vision.

This is particularly significant because it is now evident that cumulative blue light exposure contributes to the development of Age-related Macular Degeneration (AMD), the leading cause of blindness in the developed world. As blue light wavelengths are not beneficial for light therapy, the use of blue or blue-enhanced light therapy lamps can only increase the risk of vision loss, without any offsetting potential benefit.
See the risk of ocular damage from the use of bright light or blue light therapy devices.
and A Logically Sufficient Basis for Establishing that Blue Light Contributes to the Development of AMD.

For information on earlier studies which found increasing the proportion of blue light in light therapy devices is of no benefit for light therapy, please (See Ref) and (Editorial in Sleep Med 2009)

Mis-Understandings used to Justify increased Levels of Blue Light in Light Therapy.

Note: The theoretical understandings on which blue light therapy was based, i.e. that the absorption spectrum of melanopsin in intrinsically photosensitive ganglion cells in the mammalian retina determines the spectral sensitivity of the photic pathway from the retina to centers of the brain not involved in vision, have been found to be ill-conceived and are now being re-assessed. As the authors of a recent paper in Neuron stated, "our data suggest a relatively simple segregation of photoreceptor inputs to NIF (nonimage forming) vision under field conditions. They predict that rods play the predominant role in driving responses at night and around dawn/dusk with melanopsin taking over throughout most daylight."³
More recently, in Nature Neuroscience (Published online 15 August 2010), Altimus et al. found "At low light intensity, ipRGCs lack sensitivity, whereas rods are known to respond to increasing light levels and thus reliably relay this information to higher centers. Rods will continue to signal persistent light exposure through the rod-cone pathway even under conditions where their photocurrent is saturated. Finally, at high light intensities and for prolonged light exposures, melanopsin phototransduction in ipRGCs will extend the range of light intensities that allow circadian photoentrainment." ⁴ These new studies, although conducted on mice, support the finding of Sunnex Biotechnologies earlier studies on the spectral sensitivity of humans, and help explain the effectiveness of the patented low intensity GreenLIGHT technology used in Lo-LIGHT lamps.

¹ CHRIS BICKEL/SCIENCE TRANSLATIONAL MEDICINE
² See Spectral Responses of the Human Circadian System Depend on the Irradiance and Duration of Exposure to Light. Science Translational Medicine, May 2010
³ Distinct Contributions of Rod, Cone, and Melanopsin Photoreceptors to Encoding Irradiance. Neuron May 13, 2010; 66:417-428. Lall, Lucas et al
⁴ Rod Photoreceptors Drive Circadian Photoentrainment across a Wide Range of Light Intensities. Nature Neuroscience; in press August 15, 2010; Altimus, Hatar et al

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