Light regulates the 24-hour sleep-wake cycle in healthy humans. Typically, the body's temperature is high during the day, allowing people to remain alert and active. The temperature is low at night, which facilitates sleep.
But those with Alzheimer's disease often wake up numerous times at night causing them to fall asleep more often during the day. The major result is nighttime wandering, a top factor in why patients are institutionalized.
Figueiro's team conducted the light study for 30 days 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 maximally effective at affecting the circadian system whereas middle wavelengths (yellow-green) are better for visual performance. The circadian system is composed rhythms that repeat at approximately every 24 hours.
Four Alzheimer's patients were exposed to about 20 watts of blue LED lighting two hours before bedtime, 6- 8 p.m., for two 10-day periods. Red LEDs were used to control for placebo effects.
Figueiro's team found that blue light exposure delayed the decline of the patients' body temperatures by two hours. In other words, they slept better between two and four hours after the light exposure. Furthermore, the two patients who wore the 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.
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Contact: Megan Galbraith
galbrm@rpi.edu
518-276-6050
Rensselaer Polytechnic Institute
25-Sep-2002