Patients with Alzheimer's disease sleep better through the night if they are exposed to blue LED lighting a few hours before they go to bed, according to researchers at Rensselaer Polytechnic Institute.

Light regulates the 24-hour sleep-wake cycle in humans. Normally, body temperature is high during the day, which helps people stay active and alert. The body temperature drops at night, promoting sleep.

Alzheimer's disease patients often wake up throughout the night, causing them to sleep more during the day. This activity results in nighttime wandering, which is one of the main reasons these patients are put in nursing homes.

Researchers conducted a 30-day light study at a residential and adult day care center. Blue LEDs (light-emitting diodes) were used for the study as research has shown that this type of light is most effective in affecting the circadian system, which is composed of rhythms that repeat approximately every 24 hours.

Four Alzheimer's patients were exposed to about 20 watts of blue LED lighting two hours before bedtime for two 10-day periods. Red LEDs were used on a control group to test for a placebo effect.

Blue light exposure delayed the decline of the patients' body temperatures by two hours, causing them to sleep better between two and four hours after exposure to the light. Two patients who wore wrist activity monitors showed more activity during daylight than at night.

Researchers plan to repeat the study in a larger group of Alzheimer's disease patients to confirm their findings.

Other sources: Rensselaer Polytechnic Institute