Nihon Ika Daigaku zasshiAug 31, 1999

Bright light’s effects on thinking problems in Alzheimer’s dementia

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Apr 6, 2026

Abstract

Bright light therapy improved cognitive functions in patients with Alzheimer-type dementia, particularly in those with questionable and mild stages.

Twenty-seven patients with Alzheimer-type dementia received morning bright light therapy for 4 weeks.
Circadian rhythms showed improvement following bright light therapy, as measured by actigraphy.
Cognitive functions, assessed by the Mini-Mental-State Examination (MMSE) and Alzheimer's Disease Assessment Scale (ADAS), improved post-therapy.
The most notable enhancements in cognitive function were observed in memory and behavior, particularly for patients with questionable and mild dementia.
No significant effect on the overall severity of dementia was found.

Simplified

We investigated the effectiveness of bright light therapy on cognitive disturbances and its effect on circadian (sleep-wake) rhythm in Alzheimer-type dementia (ATD). Twenty-seven patients with ATD were treated with bright light therapy in the morning for 4 consecutive weeks. We evaluated the cognitive functions and circadian rhythms of the patients as a whale, and as members of two groups (one: questionable and mild dementia: the other: moderate and severe dementia; both groups classified by the severity criteria of Clinical Dementia Rating). We assessed circadian rhythms by actigraphy and cognitive states by Mini-Mental-State Examination (MMSE) and Alzheimer's Disease Assessment Scale (ADAS) before and after light therapy. Bright light therapy improved circadian rhythm. Although bright light therapy had no Significant effect on the Severity of dementia, it improved the MMSE scores, cognitive functions of ADAS scores (memory > language) and non-cognitive functions of ADAS scores (behavior = mood), especially in the questionable and mild dementia group. These results suggest that bright light therapy improves cognitive functions with the modification of circadian rhythm, especially in the early stages of ATD.

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Bright light’s effects on thinking problems in Alzheimer’s dementia

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