Effects of bright light on cognitive and sleep-wake (circadian) rhythm disturbances in Alzheimer-type dementia

Twenty-seven patients with Alzheimer-type dementia (ATD) were treated with bright light therapy in the morning for four consecutive weeks. The cogniti ve state of each patient was evaluated with the Mini-Mental-State Examinati on (MMSE) and circadian rhythm with actigram before and after therapy for a il of the patients and those of two groups divided by the severity criteria of the Clinical Dementia Rating. The therapy improved the circadian rhythm disturbances. Although the therapy caused no remarkable effects on dementi a severity, it improved the MMSE scores,especially in the early stages of A TD. These results suggest that bright light therapy improved the circadian rhythm disturbances and then bettered the cognitive state in early-stage AT D.