These data indicate that Alzheimer's disease causes disturbances of circadian rhythms and that sundowning is related to a phase delay of body temperature caused by Alzheimer's disease.

Alzhein. er s disease (AD) causes sleep and behavioral disturbar es which may be related to abnormalities of circadian .-hythms caused by damage ofthe suprachiasmatic nuc,'eis. Exposure to bright light may compensate for this danlage by improving synchronization, timing and amplijude ofcircadian rhythms. Three case studies, presented n this paper, demonstrate the beneficial effect oflight th rapy on sleep and one ofthe cases also suggests that .ight therapy may be effective in the treatment ofagitateoJ behavior The clinical observations also suggest a net " for increased level oflighting in long term care facili its. Introdu w-tionThe cotinection between sleep and wake behaviors is dependent upon closely synchronized biological rhythms, such as boidy temperature changes and adrenal cortex secretion. The suprachiasmatic nucleus (SCN) in the hypothala mius is the key to balancing the body's rhythms of sleep-wil..ke, core body temperature, and concentration