Impact of ambient bright light on agitation in dementia

Int J Geriatr Psychiatry. 2010 Oct;25(10):1013-21. doi: 10.1002/gps.2453.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Aged, 80 and over
  • Dementia / complications*
  • Dementia / diagnosis
  • Female
  • Humans
  • Institutionalization
  • Lighting*
  • Logistic Models
  • Male
  • Middle Aged
  • Phototherapy / methods*
  • Psychomotor Agitation / etiology
  • Psychomotor Agitation / therapy*
  • Time Factors