Light For Alzheimer's Disease

   Light is an important nutrient for human beings. Light regulates our entire well-being through circadian rhythms. From the time you wake up to the time you go to bed again, your body functions are regulated according to a rigid schedule,and this schedule revolves around the 24 hour day. For example, the normal daily rhythm of heart rate and blood pressure is to rise during the day and reach lows during the early night and morning. Alzheimer patients do not have normal circadian rhythms. Their blood pressure does not drop at night as is normal [107-108]. Further, their heart rate does not drop at night [109]. There are two reasons that might explain why daily rhythms are disturbed in alzheimer's disease. First, mice that have high levels of amyloid beta have disturbed daily rhythms. Those without overexpressed amyloid beta have normal rhythms. Something about amyloid beta triggers disrupted rhythms [110].Second, the area of the brain that controls the daily rhythms of life, the suprachiasmatic nucleus, loses brain cells during the course of alzheimer's disease [111].
    External bright light can be very therapeutic for alzheimer patients. Because the daily rhythms of alzheimer patients are disrupted, many of these patients sleep during the day and stay awake at night. When these patients are exposed to bright light daily, their rhythms return to normal, and they sleep normally at night [112]. Bright light also reduces the incidence of agitation in alzheimer patients [113]. One study recently reported that bright light therapy increases Mini Mental State Exam scores in patients [114]. The best way to make sure patients get bright light is to take them outside in the sun daily, even if briefly. Studies have shown that alzheimer patients get far less exposure to the sun than do non-demented elderly [115].

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