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Contact:   Rebekah Mullaney
Lighting Research Center
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mullar2@rpi.edu
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Troy, N.Y. -  7/17/2012

Exposure to Light Could Help Alzheimer's Patients Sleep Better

New Study From the Lighting Research Center at Rensselaer is the First To Collect Circadian Light Exposure and Activity Data in Individuals With Alzheimer's Disease

Individuals with Alzheimer’s disease and related dementias (ADRD) often sleep during the day and are awake at night. The situation can turn life-threatening if they leave their homes and wander around outside. This irregular sleep schedule and night wandering, and the consequent burden on their caretakers, is a primary reason individuals with ADRD are placed in more controlled environments such as nursing homes. A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute lays the foundation for the importance of tailored light exposures as a viable treatment option for the reduction of sleep disturbances in older adults and those with ADRD.
 
Funded by a R01 grant from the National Institute on Aging (NIA), the study is the first to collect circadian light exposures in individuals with ADRD. Results of the quantitative study show that individuals with ADRD experienced lower light levels, exhibited lower activity levels, and had greater disruption to their natural circadian rhythms than healthy older adults. The findings also show that people with ADRD experience lower levels of light exposure and greater levels of circadian disruption during the winter.
 
“We used light/dark and activity/rest patterns to assess circadian disruption and our results are consistent with previous studies. However, this is the first field study to examine the synchrony between the circadian light pattern and the activity response pattern to assess circadian disruption,” said Mariana Figueiro, associate professor at Rensselaer and director of the Light and Health Program at the LRC, who led the study. “Measurements revealed that those with ADRD experienced more circadian disruption than healthy older adults.”
 
Results of the study, titled “Field Measurements of Light Exposures and Circadian Disruption in Two Populations of Older Adults,” will appear in the Journal of Alzheimer’s Disease. Figueiro presented the research team’s findings at the Alzheimer’s Association International Conference in Vancouver on July 17.
 
Along with Figueiro, co-authors of the study are LRC Director and Professor Mark S. Rea, LRC Research Specialist Robert Hamner, Patricia Higgins, professor at Case Western Reserve University, and Dr. Thomas Hornick, Associate Director of the Geriatric Research Education and Clinical Center at the Louis Stokes Cleveland VA Medical Center and professor at Case Western Reserve University.
 
Growing evidence indicates that circadian disruption by irregular light/dark patterns is associated with reduced quality of life and increased risk of disease. Circadian rhythms are governed by the human body’s master clock in what is known as the suprachiasmatic nuclei (SCN), which has an intrinsic period slightly longer than 24 hours. On average, the SCN runs with a period of 24.2 hours. Light/dark patterns on the retina, the photosensitive part of the eye, synchronizes the SCN to the 24-hour solar day, regulating biological rhythms such as when we are active and when we sleep. Without exposure to a regular, daily pattern of light and dark, circadian rhythms can become irregular.
 
“Biology is driven by circadian rhythms at every level, and light is the main stimulus for synchronizing the circadian system to the solar day. By quantifying an individual’s light/dark exposure pattern, we can prescribe ‘light treatments’ promoting circadian entrainment, thereby improving health and well-being,” said Figueiro.
 
To collect data for the study, the research team used a Dimesimeter, a dime-sized device developed by the LRC, to record how much photopic and circadian light an individual is exposed to and whether they are active or resting. The data-logging device records these light and activity levels continuously over many days, and can be easily attached to shirt collars, lapels, hats, wristbands, or eyeglasses. The Dimesimeter enables researchers to examine light/dark and activity/rest patterns in those experiencing circadian sleep disorders, such as Alzheimer’s patients. Data from the device can be downloaded to a computer and processed to calculate a cross-correlation of the activity/rest and light/dark exposure data, a measure of circadian entrainment/disruption.
 
“The Dimesimeter system allows researchers to accurately measure light/dark exposure and activity/rest patterns to quantify circadian disruption. In this way, we can collect ecological data on populations who suffer from circadian sleep disorders,” said Rea. “This new study using the Dimesimeter is a major step toward the goal of better understanding the impact of circadian disruption on human health.”
 
For the new NIA-funded study, the research team enlisted 16 healthy older adults and 21 adults with ADRD to wear a Dimesimeter on their wrists for one week.The research team in Cleveland collected data from those with ADRD and the research team in Troy collected the data from healthy older adults. From the resulting data, the researchers calculated two metrics for each subject: relative activity (RA) to measure activity, and phasor magnitude to measure both light exposure and activity. The analysis revealed that during winter, those with ADRD exhibited more circadian disruption than healthy adults as reflected by their significantly shorter phasor magnitudes and lower RA values. Those with ADRD studied in winter also had significantly shorter phasor magnitudes than those studied in summer. ADRD adults were less active during waking hours than healthy adults, and ADRD adults studied in winter were exposed to less light than healthy adults in winter and ADRD adults in summer. The research team is currently delivering a lighting intervention to those with ADRD and their caretakers and measuring its impact on their sleep efficiency and circadian disruption.
 
Looking forward, the Dimesimeter could one day allow physicians to predict the optimum timing of the light therapy necessary to resynchronize the circadian phase with the solar day. Such treatments could range from going outdoors for 15 minutes to sitting in front of a light box fitted with blue LEDs for a prescribed amount of time, according to Figueiro.
 
Last year, international magazine The Scientist named the LRC’s Dimesimeter as one of the “Top 10 Innovations of 2011.”
 
About the National Institute on Aging (NIA)
NIA, one of the 27 Institutes and Centers of the National Institutes of Health, leads the federal government in conducting and supporting research on aging and the health and well-being of older people. The Institute seeks to understand the nature of aging and the aging process, and diseases and conditions associated with growing older, in order to extend the healthy, active years of life. In 1974, Congress granted authority to form NIA to provide leadership in aging research, training, health information dissemination, and other programs relevant to aging and older people. Subsequent amendments to this legislation designated NIA as the primary Federal agency on Alzheimer’s disease research. For more information, please visit www.nia.nih.gov.

 


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 has been pioneering research in energy and the environment, light and health, transportation lighting and safety, and solid-state lighting for more than 25 years.
In 1990, the LRC became the first university research center to offer graduate degrees in lighting and today the LRC offers both a M.S. in lighting as well as a Ph.D. to educate future leaders in lighting. Internationally recognized as the preeminent source for objective information on all aspects of lighting technology and application, LRC researchers conduct independent, third-party testing of lighting products in the LRC's state of the art photometric laboratories, the only university lighting laboratories accredited by the National Voluntary Laboratory Accreditation Program (NVLAP Lab Code: 200480-0). LRC researchers are continuously working to develop new and better ways to measure the value of light and lighting systems, such as the effect of light on human health, and the effect of light on plant physiology.
The LRC believes that by accurately matching the lighting technology and application to the needs of the end user, it is possible to design lighting that benefits both society and the environment.

About Rensselaer Polytechnic Institute
Rensselaer Polytechnic Institute, founded in 1824, is the nation's oldest technological university. The university offers bachelor's, master's, and doctoral degrees in engineering, the sciences, information technology, architecture, management, and the humanities and social sciences. Institute programs serve undergraduates, graduate students, and working professionals around the world. Rensselaer faculty are known for pre-eminence in research conducted in a wide range of fields, with particular emphasis in biotechnology, nanotechnology, information technology, and the media arts and technology. The Institute is well known for its success in the transfer of technology from the laboratory to the marketplace so that new discoveries and inventions benefit human life, protect the environment, and strengthen economic development.