Impact of ambient bright light on agitation in dementia

OBJECTIVE: To evaluate the effect of ambient bright light therapy (BLT) on agitation among institutionalized persons with dementia. METHODS: High intensity, low glare ambient lighting was installed in activity and dining areas of a state psychiatric hospital unit in North Carolina and a dementia-specific residential care facility in Oregon. The study employed a cluster-unit crossover design involving four ambient lighting conditions: AM bright light, PM bright light, All Day bright light, and Standard light. Sixty-six older persons with dementia participated. Outcome measures included direct observation by research personnel and completion by staff caregivers of the 14-item, short form of the Cohen-Mansfield Agitation Inventory (CMAI). RESULTS: Analyses of observational data revealed that for participants with mild/moderate dementia, agitation was higher under AM light (p = 0.003), PM light (p < 0.001), and All Day light (p = 0.001) than Standard light. There was also a trend toward severely demented participants being more agitated during AM light than Standard light (p = 0.053). Analysis of CMAI data identified differing responses by site: the North Carolina site significantly increased agitation under AM light (p = 0.002) and PM light (p = 0.013) compared with All Day light while in Oregon, agitation was higher for All Day light compared to AM light (p = 0.030). In no comparison was agitation significantly lower under any therapeutic condition, in comparison to Standard lighting. CONCLUSIONS: Ambient bright light is not effective in reducing agitation in dementia and may exacerbate this behavioral symptom.