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Troy, NY -  9/23/2002

Lighting Research Center Probing Key to Good Night's Sleep for Persons with Alzheimer's

The results of a recent pilot study by LRC researchers has found that Alzheimer's patients sleep better through the night when they are first exposed to blue LED lighting a few hours before going to bed. Mariana Figueiro led the team conducting the study.

"Light regulates circadian system in healthy humans," said Figueiro. The circadian system, which controls the sleep-wake cycle, is composed of rhythms that repeat about every 24 hours. "The body's temperature is typically high during the day, which allows people to remain alert and active. At night, the temperature is lower, which facilitates sleep."

People with Alzheimer's disease, according to Figueiro, often wake up repeatedly through the night, causing them to fall asleep more often during the day. One of the most serious results is nighttime wandering, which is often the reason Alzheimer's patients are institutionalized.

Figueiro's team conducted the 30-day light study at the Schuyler Ridge Residential and Adult Day Health Care Center in Clifton Park. The team chose blue LEDs (light-emitting diodes) because recent research has shown that short wavelength (blue) light is most effective at affecting the circadian system. Middle wavelengths (yellow-green) are better for visual performance.

Four Alzheimer's patients were exposed to about 20 watts of blue LED lighting two hours before bedtime, from 6 - 8 p.m., for two 10-day periods. Red LEDs were used as a control for placebo effects. The team found that blue light exposure delayed the decline of the patients' body temperatures by two hours, helping them to sleep better between two and four hours after the light exposure. Two patients who wore wrist activity monitors showed more activity during daylight than at night. To confirm these findings, the LRC plans to replicate this study in a larger population.

An article about the study is being published in the journal, Sleep Review. For more information, contact Mariana Figueiro at 518-687-7142 or email

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 solid-state lighting, light and health, transportation lighting and safety, energy efficiency, and plant pathology. 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. With 35 full-time faculty and staff, 15 graduate students, and a 30,000 sq. ft. laboratory space, the LRC is the largest university-based lighting research and education organization in the world.

About Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute, founded in 1824, is America's first technological research university. The university offers bachelor's, master's, and doctoral degrees in engineering; the sciences; information technology and web sciences; architecture; management; and the arts, humanities, and social sciences. Rensselaer faculty advance research in a wide range of fields, with an emphasis on biotechnology, nanotechnology, computational science and engineering, data science, and the media arts and technology. The Institute has an established record of success in the transfer of technology from the laboratory to the marketplace, fulfilling its founding mission of applying science "to the common purposes of life."