 LRC Presents at International Conference on Effects of Light on Human Well-being
Experiencing LIGHT 2009 was an international two-day scientific conference in Eindhoven, The Netherlands, for those interested in the effects of light and light design on human well-being including mood, emotions, subjective and objective health, comfort, atmosphere perception, productivity and performance. The October event was the first international conference with a major focus on the psychological processes related to the perception of and exposure to both natural and electric lighting.
Two LRC conference submissions were accepted and presented at the event. Following are summaries of each.
New ecological measurement and analysis techniques
The LRC’s Daysimeter™ device—a small, head-mounted device designed to measure an individual’s daily rest and activity patterns, as well as exposure to circadian light—continues to be used in various studies examining the impact of light on human health and well-being. New data analysis techniques further demonstrate the strength and necessity of this device in understanding behavioral circadian entrainment/disruption.
The Daysimeter has two light sensors near the eye to estimate circadian stimulus exposures over
extended periods of time. A measurement technique called phasor analysis, based on signal processing, creates circular cross-correlations of activity and light exposure data to better interpret the results sampled together over consecutive multiple days in terms of the phase and magnitude of the joint 24-hour patterns.
This combining of measured periodic activity-rest patterns with the measured periodic light-dark patterns enables scientists to better assess behavioral circadian entrainment/disruption. It also enables scientists to parametrically study the impact of circadian disruption actually experienced by individuals in different living environments with any one of several animal models for human diseases and disorders.
These new ecological measurement and analysis techniques presented at the conference allow for future studies that can then serve as the next logical step in understanding the impact of circadian disruption on human health, complementing the pioneering epidemiological studies that have raised collective concern for how circadian disruption might impact human health.
 Evidence That Both Red and Blue Lights Increase Nocturnal Alertness
It is well accepted that the circadian system is maximally sensitive to short-wavelength (blue) light and is quite insensitive to long-wavelength (red) light. In a study sponsored by the Office of
Naval Research examining the effects of different lighting conditions on alertness and performance, LRC scientists found that not only blue light but also moderate levels of red light increased alertness at night.
The researchers measured the impact of nocturnal alertness using an electroencephalogram (EEG). Exposures to red and to blue light resulted in EEG rhythmic activity changes reflecting increased alertness and a reduction in relaxation relative to preceding dark conditions. Exposures to high, but not low, levels of red and of blue light also significantly increased heart rate relative to the dark conditions.
The results, presented at the conference, suggest that the circadian system is not the only light-sensitive pathway involved in determining alertness at night, and that other mechanisms may exist.
Complete conference proceedings from Experiencing LIGHT 2009 can be found at http://www.experiencinglight.nl/program.html. | 
Lighting Research Center, 21 Union Street, Troy, NY 12180 USA 
