Objective: Disturbances of circadian rest-activity rhythms in demented patients often culminate
in the clinical problem of evening and nighttime agitation. The aim of the current study was to test
the impact of a dynamic lighting system on agitation and rest-activity cycles in patients with dementia.
Methods: From midwinter on, a ceiling mounted dynamic lighting system was installed in the common
room of a nursing home and programmed to produce high illuminance with higher blue light proportions
during the day and lower illuminance without blue light in the evening. Fifteen residents with dementia
were regularly assessed with the Cohen Mansfield Agitation Index (CMAI) before and after the lighting
intervention. Additionally rest-activity cycles were continuously monitored for 6 months by a wrist
worn activity watch. Analysis of CMAI data was performed by using the Wilcoxon-Test for matched
pairs (before vs. after the lighting installation). Rest-activity data was compared with t-tests for dependent
The dynamic lighting significantly reduced the CMAI sum-scores from 30.2±5.1 to 27.9±2.6 (mean ±
SD; N = 12; p<0.05). Analysis of the CMAI subscores revealed that under the dynamic lighting mainly
non-physically aggressive behaviors were reduced.
Results: Results from the rest-activity analysis did not show differences of circadian amplitude and
other circadian variables before and after the lighting installation.
The dynamic lighting in the living room significantly reduced agitated behavior in demented patients,
indicating short-term benefits from higher daily light exposures. Whether such lighting also impacts
long-term (circadian) rest-activity cycles needs to be further investigated.