Current research indicates that daily patterns of light exposures, through the melanopsin-containing retinal ganglion cell (mc-RGC) pathway, has a profound effect on both acute brain function and daily entrainment of circadian physiology. Our night-time exposures to artificial lighting are disruptive of circadian physiology as shown in controlled sleep studies and studies on shift-workers, particularly irregular shift work. Disruption of circadian physiology acutely affects alertness and cognitive function. Chronic circadian disruption has been linked to increased incidence of cancer, metabolic syndrome, and a wide spectrum of neuro-psychiatric dysfunction. Modern life is increasingly characterized by long periods of indoor activities during both day and night for which the same conventional lighting standards are applied. These standards are based on color vision sensitivity regardless of mc-rgc pathway activation. This tends to fragment the normal diurnal pattern of spectral irradiance and may be leading to widespread alterations in circadian physiological stresses. Consequently, one might improve both health and productivity of our modern populace by temporally altering the artificial light spectrum to increase mc-rgc activation (blue-light enrichment) during the daytime and decreasing it at night (diminished blue component). We have been searching for simple ways to test this hypothesis and to provide practical means for individual optimization given the wide range of real-world ambient light exposure patterns. Fluorescent lighting and more recently LED lighting are capable of greatly enriching the blue spectrum by increasing the amount of primary blue light transmitted through the phosphors that create the output white light. For example, recent studies suggest that daytime exposure to bright high-color-temperature (blue-enriched) fluorescent lights in daytime common rooms of patients with dementia led to decreased rate of long-term decline in cognitive function. Any standard light that increases daytime melanopsin activation will also lead to disruption when used at night. For the general population, we believe circadian disruption from such blue-light rich artificial lights at night is a major problem. To optimize circadian health in the modern urban world, we hypothesize will require temporal control of the artificial light spectrum. Computer monitors (and televisions) are universally designed to exceed ambient light levels reaching the retina (hence dominate mc-rgc pathway activation when used. In our modern society, large segments of the population average 4 hours of computer use per day. Similarly televisions are on typically up to 8 hours in an average American household. These high brightness sources on which we routinely fixate for long periods are the most likely light to be altering natural patterns of activation of melanopsin-containing retinal ganglion cells and their projections to the brain. However, modern computer monitors and digital televisions provide a path to dynamically control mc-rgc activation relative to color vision sensitivity by altering the RGB gain structure. We have developed dynamic color balance software that can control the color balance over a diurnal cycle to vary mc-rgc activation 10 fold while keeping photopic sensitivity constant. Our hypothesis is that daily computer use is having a measurable effect on circadian physiology. By using dynamic control of the RGB balance with easily exported software, we hope to develop computer based real-world testbeds to measure such acute effects on alertness and cognitive function throughout the day. Using the diurnal records of performance for a given individuals might eventually be use to self-optimize the temporal pattern of artificial light spectra for a given individual which is affected by both their other daily environmental zeitgebers and likely the genetic variations in their circadian systems physiology. We are currently trying to integrate our spectral-temporal control of LED/LCD computer monitors and smartphones with computerized attention, response time, cognitive function and productivity tests. We would use the subjects epersonal computer to log these data results along with those from computer-based questionnaires presented at regular intervals. With this combined testbed, we plan to design new research into lighting spectral-temporal control optimization for health in real-world systems readily exportable to office and home environments. We are considering the potential for such systems to perform anonymized studies (subject selected username and password) to provide low cost large cohort studies that provide the potential for individual feedback to reinforce behaviors that improve circadian health and performance. In collaboration with the Lighting Division of Lawrence Berkeley National Lab and the California Lighting Research Center under a DOE FLEMP grant, we have developed programmable low-level temporal and spectral control of computer monitor luminance that is compatible with the normal function of other computer programs both for cognitive function testing and for normal computer uses at work and at home.
