Lighting Research Center
LRC Intranet Web mail Lighting Research Center

Press Release


Back To Newsroom

News from the Lighting Research Center
                             Rensselaer Polytechnic Institute

Contact:   Rebekah Mullaney
Lighting Research Center
(518) 276-7118
  Newsroom Home
  Project Posters
  In the News
  About Us
  Contact Us
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 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.