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.