The effect of ambient bright light therapy on depressive symptoms in persons with dementia.

OBJECTIVES

To assess the effect of ambient bright light therapy on depressive symptoms in persons with dementia.

DESIGN

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

SETTING

The common areas of two geriatric units in a state-operated psychiatric hospital in North Carolina and in a dementia-specific residential care facility in Oregon.

PARTICIPANTS

Sixty-six older adults with dementia.

INTERVENTION

Ambient bright light therapy was delivered through a high-intensity, low-glare lighting system installed in the public areas of study units at both sites. Each lighting condition was provided for multiple 3-week periods in a predetermined sequence.

MEASUREMENTS

Staff caregivers completed the Cornell Scale for Depression in Dementia (CSDD) in the last week of each 3-week period to provide information about participants' moods.

RESULTS

Analysis indicated a sex-by-treatment interaction (P=.008). Significant sex differences were found in CSDD scores in response to evening light (P=.003), all-day light (P=.001), and standard light (P</=.001). Depressive symptoms were lowest for women and highest for men during morning light.

CONCLUSION

Findings do not support the use of ambient bright light therapy as a treatment for depressive symptoms in persons with dementia, although a subpopulation of persons with dementia may benefit from this intervention. It is likely that individual rather than unit-level interventions are a more effective strategy for delivering bright light therapy for this population.