Care of patients with dementia requires dynamic, creative approaches. Given the high incidence of sleep-wake disturbances in this population and the concomitant caregiver stress and institutionalization, researchers at the Geriatric Research Education and Clinical Center (GRECC) at the Louis Stokes Cleveland (LSC) VAMC in Ohio are exploring light as a nonpharmacologic intervention to improve sleep-wake activity in veterans with dementia.1
Light has a powerful physiologic effect on human circadian rhythms, and those who live in northern latitudes or spend long periods inside buildings often have limited exposure to dramatic light-dark differences required for circadian entrainment to the solar day. This article is intended to give a brief overview of the relationship between light and human health and describe initial pilot studies in improving rest-activity patterns through lighting.
Light and the Aging Eye
Light is received at the back of the eye and absorbed by retinal cells, rods, and cones and by intrinsically photosensitive retinal ganglion cells that are specialized circadian light receptors. These specialized receptors respond most strongly to short-wavelength (blue) light. Nerve pathways lead from the retina to the suprachiasmatic nucleus, the circadian pacemaker, influencing the secretion and suppression of biomarkers, such as melatonin, cortisol, and hypocretin.2 Many hormonal systems, including the steroid axis, key on this 24-hour cycle that seems to be partially timed via the hormone melatonin.
Serum melatonin signals darkness and nighttime to the body. It rises in the early evening, peaks in the middle of the night, and is low during the daytime hours. Light exposure at night can suppress melatonin, which can in turn alter the timing of circadian rhythm peaks and troughs.
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Normal aging of the eye can include good acuity. Most older adults retain 20/25 or better vision in 1 eye into their 70s and 80s. However, changes in the anatomy of the eye due to aging can reduce contrast sensitivity, color vision, and visual fields. Reduction of light to the retina due to these normal physiologic changes can impair the response to circadian light. By the eighth and ninth decades of life, the amount of circadian activating light reaching the retina is one-tenth that for a 10 year old; thus, brighter white light or more short-wavelength light is needed.3
In addition to the anatomic changes in the eye, a muted 24-hour light exposure pattern contributes to circadian disruption in older adults. For those with dementia, the circadian disruption is manifested in rest-activity disorders, such as sundowning and day-night disorientation. Yet patients with dementia residing at home or in nursing homes routinely are exposed to subdued light patterns. For example, according to the results of a study, nursing home residents in San Diego, California, had a median of 10.5 min/d of exposure to bright light (> 1,000 lux) and median illuminance was 52 lux during daylight hours.4
How can light levels be changed to make them optimal or even sufficient for health? The researchers considered this question when opting to study light and its possible effects on older patients with dementia.
Lighting interventions in nursing homes may be effective. For example, 2 hours of bright light exposure in the morning improved sleep efficiency (number of minutes sleeping divided by number of minutes in bed).5 Furthermore, 30 minutes of sunlight per day has been shown to reduce daytime napping.6 In an investigation of long-term exposure to bright light, participants in the experimental group had less than the expected decline of their Mini-Mental State Examination scores across 3.5 years, improved depression scores, and less functional decline in their activities of daily living.7 Thus, lighting may have therapeutic effects for institutionalized patients with dementia, particularly if there is prolonged exposure.
Although increasing light levels improves rest-activity patterns in those with dementia, implementation and adherence is a challenge due to discomfort and glare, difficulty maintaining the level of light exposure due to a person’s activity, and/or energy codes that restrict power consumption in nursing homes. Although many human studies have used mixed spectrum light at high light levels, evidence suggests that the circadian system is maximally sensitive to shorter wavelength blue light.8 Therefore, short-wavelength blue light can achieve the same clinical outcomes while using lower illuminations and obviating many of the issues with bright lights.
Dayroom Transformation
In “light” of this background, the LSC VAMC GRECC engaged in a transformation of a community living center (CLC) dayroom to introduce circadian lighting, determine its acceptance to patients and staff, and measure rest-activity measurements for 3 residents. The CLC ward specializes in the care of veterans with dementia and had recently undergone a cultural transformation into a neighborhood system with many activities still centered on the dayroom/dining room. Based on the research of colleagues at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute (RPI) in Troy, New York, scientists at General Electric (GE) Lighting division in Cleveland developed fluorescent lamps emitting light in the short-wavelength portion of the visible spectrum (lamps with correlated color temperature [CCT] of 14,000 kelvin [K]; typical commercial use lamps have a CCT of 3,000-5,000 K).