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J Am Geriatr Soc. 2007 Oct;55(10):1524-33. Epub 2007 Aug 21.

High-intensity environmental light in dementia: effect on sleep and activity.

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Department of Family Medicine, School of Medicine; Cecil G.Sheps Center for Health Services Research, University of North Carolina, Chapel Hill, NC, USA.



To determine whether high-intensity ambient light in public areas of long-term care facilities will improve sleeping patterns and circadian rhythms of persons with dementia.


A cluster-unit crossover intervention trial involving four conditions: morning bright light, evening bright light, all-day bright light, and minimum standard light.


The common areas of two geriatric units in a psychiatric hospital and a dementia-specific residential care facility.


Sixty-six older adults with dementia.


Ambient bright light of approximately 2,500 lux, delivered through a low-glare lighting system installed in the dining and activity areas. Participant exposure averaged 2.5 to 3.0 hours for the morning and evening interventions and 8.4 hours for the all-day intervention.


Nighttime sleep using wrist actigraphy and daytime activity using nonobtrusive daytime observations.


Night-time sleep increased significantly in participants exposed to morning and all-day light, with the increase most prominent in participants with severe or very severe dementia (mean increase 16 minutes (P=.008) for morning, and 14 minutes (P=.01) for all-day). Morning light produced a mean phase advance of 29 minutes (P=.02) and evening light a mean phase delay of 15 minutes (P=.06). Effects on daytime sleepiness were inconsistent, and the number of sleep bouts, mesor, amplitude, intradaily variability, and interdaily stability were not significantly different, indicating that the overall strength of day and night activity rhythms did not change significantly under any treatment condition.


Bright light appears to have a modest but measurable effect on sleep in this population, and ambient light may be preferable to stationary devices such as light boxes.

[Indexed for MEDLINE]

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