Advancing the effective use of light for society and the environment.

Thursday, April 14, 2005

Researchers Use Blue Light to Treat Sleep Disturbances in the Elderly
Photo: Seniors participate in blue-light treatment study
Seniors receive the experimental light treatment while playing cards in the residence dining room.

In a recent pilot study, scientists at the Lighting Research Center demonstrated how exposure to blue light can reduce sleep disturbances and increase the likelihood of stable, consolidated sleep in seniors. The study included subjects with Alzheimer’s disease (AD), an illness often accompanied by severely irregular sleep/wake patterns, as well as those without dementia who simply have trouble sleeping.

The occurrence of sleep disturbances increases as we age. Researchers have long believed the disturbances often result from a disruption of the body’s circadian rhythms—biological cycles that repeat approximately every 24 hours, including the sleep/wake cycle.

“Our circadian rhythms are synchronized by the 24-hour light/dark cycle, and exposure to light and dark stimuli help to set the body’s internal ‘master clock’ to match the solar day,” says LRC light and health researcher Mariana Figueiro, Ph.D., principal investigator of the sleep study. “Light stimulus travels through the retina, the light-sensitive nerve tissue lining the back wall of the eye, to reach the master clock in the brain. However, a combination of age-related changes may influence the amount and magnitude of light/dark stimulus affecting the circadian system.”

Photo: LED luminaire used for blue-light treatment in the study
The LRC designed the luminaires for the study using LEDs donated by Nichia.

Age-related influences on the circadian system

As we age, the lens in the eye thickens and the pupil shrinks, reducing the amount of light passing through to the retina. Moreover, as we age, the circadian system may require a stronger light/dark stimulus due to deteriorating neural processes in the brain. Finally, adoption of an indoor lifestyle can create an environment with little variation in light/dark intensity, resulting in a weak light/dark stimulus to the circadian system.

“Physical changes to the eye, neural changes in the brain, and lifestyle changes can mute the light/dark signal sent to the body’s master clock, presumably contributing to major sleep disturbances in seniors,” said Mark Rea, Ph.D., LRC director and co-principal investigator on the pilot study. “There needs to be a distinct, repeated pattern of light and dark to tell the circadian system the solar time.”

The power of blue

Daylight is a mixture of wavelengths dominated by short, visible wavelength light that, in isolation, gives a blue visual sensation, like the blue sky. In fact, according to Rea, blue sky is the best stimulus for the circadian system.

“Blue sky is ideal for stimulating the circadian system because it’s the right color and intensity, and it’s ‘on’ at the correct time for the right duration—the entire day,” said Rea.

Figueiro agrees that blue light is the most effective and efficient at stimulating the circadian system. However, she explains that it isn’t just the color that is important, but rather the entire 24-hour pattern of light intensity, spatial distribution, timing, and duration, all in combination with the color.

Exposure to other light colors, as well as exposure to white light, can stimulate the circadian system, but it may take longer to get the desired response and the intensity required may cause visual discomfort, according to Figueiro.

The LRC research team set out to demonstrate that exposure to blue light, followed by darkness at bedtime, would create a light/dark pattern that the circadian system would recognize and react to.

Details of the pilot study

The research team studied the effects of blue-light treatment on seniors at a skilled nursing facility in upstate New York. In the four-week study, the residents were exposed to tabletop LED luminaires for two hours every day from 6:30 p.m. to 8:30 p.m.

For the first two weeks, one group composed of both AD and non-AD residents was exposed to blue LEDs, while another group of both AD and non-AD residents was exposed to red LEDs, a condition introduced as a placebo control. While the circadian system responds best to blue light, it is essentially non-responsive to long-wavelength radiation (red light), according to Figueiro.

After a short break, the second two-week phase of the experiment began. The residents exposed to blue light in the first phase were exposed to red light in the second phase, and vice versa.

Blue-light treatment results in longer sleep intervals

Over the course of the experimental light treatment, the research team analyzed the percentage of time the subjects slept between midnight and 6 a.m. The study showed statistically significant increases in sleep after blue-light treatment during this period for all subjects.

The non-AD subjects were found asleep 90 percent of the time between midnight and 6:00 a.m. after blue light exposure and only 67 percent of the time after red light (placebo) exposure. The AD subjects exposed to the blue-light treatment were found asleep 67 percent of the time compared to AD subjects exposed to the placebo treatment who were found asleep only 54 percent of the time.

The non-AD subjects’ stronger response to the blue-light treatment was expected, according to Figueiro, as AD patients have more fragmented sleep patterns than healthy older adults.

Next steps

Figueiro had previously studied the effects of blue light exposure on the sleep efficiency of AD subjects in 2002, but this recent pilot study was the first time she tested the theory on non-AD subjects having sleep problems.

“It was exciting to replicate our earlier study and expand our research to include non-AD subjects in order to demonstrate that blue-light treatment can have a significant, positive effect on the sleep efficiency of older adults,” said Figueiro. “The consistencies in our research support the theory that blue light can be a powerful, non-pharmacological treatment for sleep disorders in seniors and should be considered in the design and operation of senior housing.”

The LRC is pursuing additional funding for further research on the subject and hopes to motivate manufacturers to design luminaires that can be attached to glasses, television sets, or computer screens for the purpose of providing light treatment for those with sleep disorders, according to Rea.

The study was sponsored by the Alliance for Solid-State Illumination Systems and Technologies (ASSIST). The LEDs were provided by Nichia America Corp., and the luminaires were custom-built by the LRC.

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.



2005 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

Rennselear Polytechnic Institute