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.