Light Therapy May Brighten Alzheimer’s Disease Outcomes

Light Therapy May Brighten Alzheimer’s Disease Outcomes

Focused light therapy may improve sleep and reduce symptoms of depression and agitation in patients with Alzheimer’s disease (AD) and related dementias, new research suggests.

A small study of 46 participants showed that a higher level of light was significantly associated with improved sleep quality scores from baseline and vs a lower level of light.

The higher light level intervention was also associated with decreased symptoms of depression and agitation — both of which are often part of AD and related dementias.

“If you control the [light] stimulus and you know you’re actually delivering that stimulus to the patient, you can see improvement in sleep, and of mood and behavior,” principal investigator Mariana G. Figueiro, PhD, director of the Lighting Research Center and professor of architecture at Rensselaer Polytechnic Institute, Troy, New York, told.

The findings were published in the December issue of the Journal of Clinical Sleep Medicine.

“Wrong Signals”

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Significant sleep problems are a common symptom of AD and related dementias. Patients with dementia often nap or are sleepy during the day and have a hard time sleeping through the night. They often do not get the several hours of uninterrupted sleep considered healthy and restful, the investigators note.

Those sleep problems are often primary contributors moving individuals with AD out of their homes and into care facilities, Figueiro said. Caregivers often find it impossible to care for patients who sleep only 2 or 3 hours at night and require constant monitoring when they are awake.

“It is very stressful for the caregiver,” Figueiro said.

Other common symptoms include depression and agitation, including angry outbursts, which also contribute to the need to transfer patients out of their homes.

Researchers have long believed that a disruption in circadian rhythms contributes to the sleep problems in AD patients. The type of daily light exposure regulates the sleep/wake cycle.

AD patients often do not spend much time outdoors; and the light in their homes or in care facilities is often low-level light throughout the day and night, Figueiro said.

A robust light-and-dark pattern tells the human brain when it’s day and when it’s night — and when it’s time to sleep or be awake, she added. In an environment without those distinct light patterns, the brain gets the “wrong signals.”

Lights, Study, Action

Recent findings from a Cochrane review showed no evidence that light therapy helped with sleep or behavior in AD patients. However, many of the studies included in the review did not appropriately assess whether participants were actually exposed to the light levels described in the study protocols.

Although the current investigators focused on determining whether stronger light during the day would improve sleep, they also measured whether it had any effect on symptoms of depression and agitation.

The study included residents from four assisted-living facilities and four long-term care facilities in New York and Vermont. Forty-six residents in the eight facilities completed the study.

Participants were exposed to the active intervention of higher level of light, providing a high circadian stimulus (CS), or to the control intervention of a lower light level/low CS, during daytime hours for 4 weeks. Then, after a 4-week break of no special lighting, they were exposed to the opposite level of light.

The special lighting was provided via floor lamps, small light boxes, or larger light tables that were about the size of a 70-inch television lying flat. The light sources were in the participants’ bedrooms or in common areas, depending on where individuals spent the most time.

Patients wore small light meters as chest-height pendants around their necks to monitor the level of light exposure.

Nighttime caregivers completed questionnaires on behalf of the participants to assess sleep quality, depression, and agitation symptoms.

Surprising Findings

Results showed that the high-level light had a significantly positive effect on sleep quality and decreased depression and agitation scores.

The mean score on the Pittsburgh Sleep Quality Index, the study’s primary outcome measure, was 10.3 before the active intervention vs 6.67 after (P < .001). Any score higher than 5 indicates sleep disturbances, with higher scores indicating more disturbances.

The control level of lighting also had a small, but not statistically significant, effect on sleep disturbances (mean score difference from baseline, -1.39).

Scores on the depression questionnaire also significantly changed. The mean score on the Cornell Scale for Depression in Dementia was 10.3 before the active intervention and 7.05 after (P = .04).

The mean score on the Cohen-Mansfield Agitation Inventory before the active intervention was 42.65 compared with 37.14 after, a reduction difference that was not statistically significant.

However, in all three sleep, depression, and agitation surveys, the differences between the effects of the active intervention vs the control intervention were significant (P < .001, P < .05, and P = .02, respectively).

The study’s primary aim was to gain a better understanding of how light affects sleep quality, Figueiro said. The study’s findings that light also had an effect on depression and agitation “were surprising,” she said.

Figueiro has published prior research on the potential impact of light therapy in AD patients. That research compared the active intervention only with a baseline level but did not test with exposure to lower levels of light.

The current study is valuable in that it rules out any effect of any bias in the previous research, she noted.

Figueiro recommended that AD patients have regular exposure to natural light in their homes during the day and go outside whenever possible.

“Take people for a walk. Take people outdoors,” she said.

“Striking Results”

Commenting on the findings, Keith Fargo, PhD, director of scientific outreach and programs for the Alzheimer’s Association, said the study was well done and provided impressive results.

“What’s really striking about this paper is they not only saw benefits in sleep quality, they also saw the benefits in depression and agitation,” he said.

The findings are especially encouraging because symptoms like depression and agitation can be exceptionally disruptive and the most difficult issues for family caregivers to deal with in patients with AD, Fargo added.

In addition, current treatments, including antipsychotic medications in serious cases, are dangerous for patients and can increase risk for death. “We really recommend that as a last resort only,” Fargo said.

So, solid evidence of a nondrug therapy that might be helpful is valuable, he noted.

“This appears to be quite effective. These are all very positive results,” Fargo concluded.

The study was funded by the National Institute on Aging. Figueiro reports having received research grant support from the National Institutes of Health, the Office of Naval Research, the US General Services Administration, and private companies, including Acuity Brands and Axis Lighting. Fargo has reported no relevant financial relationships.

J Clin Sleep Med. 2019;15:1757-1767.

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