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Troy, N.Y. -  11/5/2006

Lighting Research Center forming collaborative group of researchers worldwide

Daysimeter User Group will collect and share circadian data using new measuring device

The Lighting Research Center at Rensselaer Polytechnic Institute is forming a collaborative group of researchers from around the world to collect data in different lighting applications using a special light measuring device called the Daysimeter. The group’s goal is to create a cooperative forum of manufacturers, scholars, scientists, and physicians who are already working in clinical applications and work environments where photobiology and circadian light exposure could be important for health and productivity.

“The human circadian system responds to light in a dramatically different manner than the visual system,” explained Mark Rea, PhD, the director of the LRC. “Light is the main stimulus that affects the human body’s clock; circadian rhythms keep the body synchronized with the solar day.”

Studies have shown that light impacts people’s health and well-being. However, it has been nearly impossible to measure a person’s quantity and quality of circadian light exposure accurately—until now. The group will measure circadian light exposure with the Daysimeter, a field research tool developed by the LRC. The Daysimeter is the first device to characterize light accurately by measuring spectrally weighted intensity, as well as timing and duration, of circadian light entering the eye, which affects the human body’s clock. Lightweight and easy to wear, the device also measures conventional light levels and records head movements in order to differentiate between rest/sleep periods and active/awake periods.

Ultimately, the Daysimeter will enable the design of light sources, luminaires (light fixtures), and lighting techniques that help people to maintain regular circadian functions such as the sleep/wake cycle and hormone production, explained Rea. This, in turn, may improve their health.

The LRC will explore clinical and special applications in which people could benefit from lighting specially tuned to the circadian system. These include hospitals, intensive care units, and assisted care facilities where patients do not have regular exposure to daylight or darkness, as well as work environments that do not allow for customary light and dark exposures such as some military operations. </div>

"The work of the Daysimeter User Group may lead to a better understanding of many health-related issues,” said Rea. He went on to explain that those issues include: how premature infants develop; appropriate learning environments for school children; improved sleep for people with Alzheimer’s disease and their at-home caregivers; teenagers with delayed sleep phase disorder; and biophysical and epidemiological concerns for senior-care residents, night-shift workers, travelers with jet lag, and others with altered light-dark exposures and sleep patterns.

As part of the Daysimeter User Group, the LRC will participate in establishing a common protocol for the use of the Daysimeter. LRC scientists will also conduct research, demonstration, evaluation, and educational activities related to its use. The first meeting of the Daysimeter User Group is scheduled for March 7, 2007, at the LRC in Troy, N.Y. Interested parties can contact Patricia Rizzo at 518-687-7100 or

More about the Daysimeter and measuring circadian light
PHOTO: A photograph of person wearing the Daysimeter is at
Larger versions of this and other related photos are available upon request.</div>
2006: Gathering and sharing data for circadian research:


The Daysimeter: A device for measuring optical radiation as a stimulus for the human circadian system, by Andrew Bierman, Terence Klein, and Mark Rea, published in the journal Measurement Science and Technology. (

List of LRC-authored papers:

Papers on light and health, including circadian phototransduction, are available on the Light and Health Web site. (

About the Lighting Research Center
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute is the world's leading center for lighting research and education. Established in 1988 by the New York State Energy Research and Development Authority (NYSERDA), the LRC conducts research in light and human health, transportation lighting and safety, solid-state lighting, energy efficiency, and plant health. LRC lighting scientists with multidisciplinary expertise in research, technology, design, and human factors, collaborate with a global network of leading manufacturers and government agencies, developing innovative lighting solutions for projects that range from the Boeing 787 Dreamliner to U.S. Navy submarines to hospital neonatal intensive-care units. In 1990, the LRC became the first university research center to offer graduate degrees in lighting and today, offers a M.S. in lighting and a Ph.D. to educate future leaders in lighting. Learn more at

About Rensselaer Polytechnic Institute
Founded in 1824, Rensselaer Polytechnic Institute is America's first technological research university. Rensselaer encompasses five schools, 32 research centers, more than 145 academic programs, and a dynamic community made up of more than 7,900 students and more than 100,000 living alumni. Rensselaer faculty and alumni include more than 145 National Academy members, six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, and a Nobel Prize winner in Physics. With nearly 200 years of experience advancing scientific and technological knowledge, Rensselaer remains focused on addressing global challenges with a spirit of ingenuity and collaboration.