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Bright light therapy: hope for dementia.

Although Alzheimer's disease (AD) is the most common cause of dementia, it can be caused by various diseases which can damange the suprachiasmatic nucleus (SCN). The SCN, located in the hypothalamus just above the optic chiasm, controls a person's circadian rhythm. Damage to the SCN impairs one's circadian rhythm. This may be manifested: by an erratic sleep/wake cycle; by a delayed sleep phase so that a person goes to sleep very late in the night and awakens late in the morning; or by an advanced sleep phase so that a person wakes up very early in the morning and goes to sleep early at night.

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Caretakers' attempts to get the person to go to bed at a "regular" time may bring out the belligerent, agitated behavior of sundown syndrome. The disruptive behaviors that make up sundown syndrome occur from late afternoon to evening (i.e., at "sundown") in people with dementia. Agitation may take the form of rocking, wandering, pacing, and increased confusion as nighttime approaches.

Currently, tranquilizers and hypnotics are used to quiet the agitation and restlessness of sundown syndrome. Studies in recent years have found that bright light therapy can regulate sleep/wake cycles in people with dementia. Some studies suggest that bright light therapy can lessen nocturnal restless behavior by increasing sleep quality. These findings are promising since bright light can avoid side effects of medication.

Sonia Ancoli-lsreal at UCSD compared the effect of using morning bright light vs. evening bright light to improve circadian rhythm in nursing home residents with Alzheimer's disease. She found that neither morning nor evening bright light treatment improved subjects' daytime alertness or sleep quality. She did find, however, that both morning and evening bright light treatment improved the rhythmicity of sleep/wake cycles.

She theorizes that no improvement may have occurred in alertness and sleep quality because no distinction was made between subjects who had AD and subjects whose dementia was caused by other illnesses. Ancoli-lsreal cites a study by Mishima which suggests that different types of dementia may respond differently to bright light treatment. In Mishima's study, the night time activity of people with vascular dementia and AD were compared after both groups were treated with morning bright light therapy. Mishima found that people with vascular dementia had less physical activity at night after treatment while the night time activity level of people with AD remained the same.

Normally, morning bright light treatment causes sleep and wake phases to shift to an earlier time the following day. Evening bright light has the opposite effect (i.e., sleep and wake phases take place at a later time the following day). Evening bright light treatment in the Ancoli-lsreal study, caused the expected delay in subjects' sleep/wake phases but it was surprising that morning bright light treatment also caused a phase delay in sleep/wake periods rather than the expected phase advance. Ancoli-lsreal believes that this ironic finding may actually be a masked phase advance.

People with dementia typically have an advanced sleep phase going to sleep earlier and waking up earlier than the norm. The "morning" time at which Ancoli-lsreal's subjects were given bright light therapy may have in actuality been their biological "evening" thereby resulting in a phase delay rather than a phase advance.

Some researchers believe there may be no circadian rhythmicity to sundown syndrome. D.L. Bliwise studied the activity level of nine nursing home residents with dementia. The staff recorded the residents' level of agitation during a period of 12 hours. Based on the staff's observations, Bliwise et al. found that agitation and restlessness occured with the same frequency both day and night.

Normally, a person gets increasingly less exposure to bright light as he ages due to spending less time outdoors. The impaired sleep/wake schedule of people with dementia, then, may be the consequence of getting very little exposure to light during the day.

To investigate this possibility, Shocat measured the average intensity of light that residents in a nursing home received daily. They found that, on the average, residents received a light intensity of 54 lux (a bright sunny day is approximately 500 lux). Residents in their study who were able to receive higher intensities of light had fewer nighttime awakenings.

Intensifying existing indirect light (e.g., opening curtains fully) can be helpful in stabilizing circadian rhythm. E. J. van Someren found that the circadian rhythm of subjects with dementia stabilized when indirect lighting was increased in their settings.

Taking care of someone who has dementia can be an overwhelming task. Caretakers have to be constantly vigilant to make sure that the person's memory loss, impaired judgment, and difficulty remembering how to do familiar tasks does not cause harm to himself or others. Caretakers are left feeling bereft as personality changes, listlessness, depression, and social withdrawal cause the person to isolate himself. The person's impaired sleep/wake schedule may leave caretakers physically exhausted as they try to or are forced to adjust. When they are most tired at the end of the day caretakers may have to find extra energy to deal with their loved one's agitated, restless behavior from sundown syndrome.

Improving the rhythmicity of sleep and wake periods through the use of bright light therapy may make it possible for caretakers to delay or avoid placing a loved one in a nursing home.

Regina Patrick, RPSGT
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Title Annotation:SLEEP MEDICINE
Author:Patrick, Regina
Publication:FOCUS: Journal for Respiratory Care & Sleep Medicine
Date:Mar 22, 2011
Words:897
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