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Bright light therapy: hope for dementia.

Although Alzheimer's disease is the most common cause of dementia, it can be caused by various diseases which can damage the suprachiasmatic nucleus, the structure controlling a person'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.

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. Belligerence may be simply stubbornness to, at worst, striking out at caregivers.

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.

Sonia Ancoli-Isreal et al of the University of California at San Diego 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.

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-Isreal 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-Isreal believes that this finding may actually be a masked phase advance.

People with dementia typically have an advanced sleep phase so that they go to sleep earlier and wake 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 phase advance.

Some researchers believe there may be no circadian rhythmicity to sundown syndrome. D.L. Bliwise et al.3 studied the activity level of nine nursing home residents with dementia. The nursing 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.

They propose that the apparent worsening of restlessness and agitation at late afternoon and evening is the impact of the disruptive behavior on caretakers. Agitation and restlessness are less acceptable and less desired in the evening when a tired caregiver is trying to get a person to go to bed. The same behavior is more acceptable in the daytime when the person is more active and caretakers are more alert.

Normally, a person gets increasingly less exposure to bright light as he ages due to spending less time outdoors. Illness limits this even further especially if a person is in an institution or is not very mobile. The impaired sleep/wake schedule of people with dementia may be the consequence of getting very little exposure to light during the day.

To investigate this possibility, Shocat et al.4 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.

Caretakers may not be able to create light intensities at the levels used in research (e.g., 1000 lux) in a home environment. Intensifying existing indirect light (e.g., opening curtains fully) can be helpful in stabilizing the circadian rhythm. E. J. van Someren et al.5 found that the circadian rhythm of 22 subjects with dementia subjects stabilized when indirect lighting was increased in their homes.

Dementia has no cure. Efforts to delay its progression often is aimed at treating a root illness (e.g., using anti-hypertensive medications to slow the progression of vascular dementia by preventing strokes); combating memory loss (e.g., using cholinesterase inhibitors to increase levels of the neurotransmitter acetylcholine which plays a role in memory); or preventing cellular damage (e.g., using the antioxidant vitamin E).

Taking care of someone who has dementia can be an overwhelming task. Caretakers to 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. Language problems and disorientation to time and space can make for frustrating communication between caretaker and the person with dementia. 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 to it. 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.

Exhaustion is the reason why many caretakers place a loved one in a nursing home. One factor feeding into the caregiver exhaustion is the impaired sleep/wake schedule of the person with dementia. 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.

by 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, 2013
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