Advancing the effective use of light for society and the environment.

Wednesday, April 26, 2006

Paper Helps Scientists Compare Light Levels Used in Cancer Studies
By Keith Toomey
Lighting studies with rodents
LEDs like those shown can be used to study the circadian system of rats and other rodents.

A new scientific paper written by Lighting Research Center scientists may help cancer researchers decode results in laboratory studies of light and cancer risk that use mice and rats. “Of mice and women: Light as a circadian stimulus in breast cancer research” will allow researchers to quantitatively compare light levels used in rodent studies with lighting conditions experienced by humans.

Lead author John Bullough, Ph.D., says this is important, because the circadian systems of nocturnal rodents are 1000-10,000 times more sensitive to light than the circadian system of humans.

“Normal room or laboratory lighting,” says Dr. Bullough, “might be a ‘dim circadian stimulus’ to a human, but would be a ‘bright circadian stimulus’ to a mouse or rat.”

The circadian system regulates biological rhythms, including the sleep/wake cycle, hormone production, and body temperature.

Drs. Mark Rea and Mariana Figueiro are co-authors of the paper.

In simple terms, the paper can serve as a "decoder ring" to help in translating lighting conditions experienced by humans in real life to those used in rodent studies. This is especially important as recent studies are beginning to show potential links between lighting (as a circadian stimulus) and cancer risk or tumor growth.

Bullough further explained that humans and nocturnal rodents also have different spectral sensitivity to light - for example, the visual and circadian systems of rats and mice are sensitive to ultraviolet radiation, whereas those of humans are not. Also the human circadian system can decode color information, while that of the mouse cannot.

The paper appears in the May 2006 issue of the journal Cancer Causes and Control. A preprint of the paper is available on the LRC Light & Health Web site.

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.

Rennselear Polytechnic Institute