Research with Alzheimer's patients suggests a 24-hour lighting regime that can improve their circadian entrainment -- improving sleep, reducing agitation and depression, and lowering the incidence of falls.
We've been discussing the effects of light on human circadian rhythms here for some time -- both the centuries-old exposure to artificial lighting at night, and the new wrinkles that LED lighting in particular brings to the issue. It turns out that a great deal of research has been performed with Alzheimer's patients to understand circadian disruption and the beneficial effects light can have to re-synchronize body rhythms with solar time.
Even healthy people, as they pass age 50, can experience a diminution of the effectiveness of the solar light-dark cycle to keep their own internal circadian rhythms in tune with the external world. For people with Alzheimer's disease and related dementias (referred to as ADRD), this diminution can be more extreme, resulting in or exacerbating random patterns of sleep and wakefulness throughout the day and night, agitation and aggressiveness, and depression. Sleep disruption, including night wakefulness, also increases the likelihood of falls.
In a paper published in the Journal of Alzheimer's Disease, Mariana Figueiro, an associate professor at RPI's Lighting Research Center, surveyed dozens of existing studies and described new research leading to the development of a 24-hour lighting scheme designed to improve the lives of people with ADRD. The lighting regime provides high circadian stimulation during the day, low circadian stimulation at night, good visual conditions during waking hours, and unique nightlights that are safe and minimize sleep disruption.
Figueiro cited 17 different studies, including two of her own, indicating that light therapy "can consolidate rest and activity patterns in people with ADRD." She noted that few of the studies used photometric instrumentation to quantify the levels of light employed (presumably her own did), instead expressing light levels in terms of photopic lux at the cornea. Exposure to bright white light (> 1,000 lux) in the morning "has been shown to improve nighttime sleep, increase daytime wakefulness, reduce evening agitation behavior, and consolidate rest/activity patterns of people with ADRD."
Also effective to various degrees in alleviating sleep-related ADRD symptoms: varying light mimicking daylight patterns, low-intensity blue light in the early evening, and all-day exposure to 4,100K white light. Such studies are complicated by the slowed response in ADRD patients to circadian cues -- some researchers believe that a study of six months may be required for any improvement in sleep patterns or other symptoms to manifest.
In general for the waking hours, Figueiro recommends lighting that is "high, on the task, glare-free with no direct or reflected view of the light source, with softer shadows throughout the space, with balanced illuminance levels, and with good color rendering characteristics."
Evening into night
For the evening hours, the recommendation is "no more than 60 lux at the cornea of a circadian-ineffective white light source (e.g., 2700K compact fluorescent lamp or LEDs)."
Figueiro has proposed a novel form of night lighting to benefit people with ADRD: low-level (5 to 10 lux at the cornea) lighting designed to "accent the rectilinear architectural features in the room," such as doorways, and to "accentuate horizontal pathways to the bathroom." She has used strips of LEDs to outline doorways and provide pathway lighting, and demonstrated in several studies that these lighting arrangements decrease the variability in step length and reduce sway as ADRD patients move about at night.
In the real world
The lighting regime Figueiro has developed will be put to real-world use at
Abe's Garden, an Alzheimer's community in Nashville, Tenn., founded to develop and disseminate evidence-based best-practices in dementia care. Board members of Abe's Garden, including Christopher Brown, CEO of the venerable lighting firm Weidenbach-Brown, helped to provide funding for the research. Brown and Scott Muse, CEO of Hubbell Lighting, are heading a fundraising effort to support ongoing research at Abe's Garden, according to a press release I received from the Alzheimer's facility (it does not seem to be online).
Alzheimer's research offers an opportunity to understand the effects of lighting on the broader population. If we know what lighting does to these people, whose circadian systems are so severely compromised, we will have a better idea what kinds of lighting ordinary people need to thrive.
— Keith Dawson , Editor-in-Chief, All LED Lighting