April 12, 2001 -- Sleep disturbance is a very common and very problematic symptom of dementia. New research indicates that causes of this sleep disturbance may differ in different kinds of dementia. Hopefully, understanding these causes will lead to better treatments.
Dementia is a term used to refer to a loss of thinking abilities. Although there are many causes of dementia, it is most often associated with aging. The most common cause of dementia associated with aging is Alzheimer's disease, which affects approximately one in 10 people over age 65 and nearly half of those over age 85.
If you have questions about Alzheimer's, check out WebMD's Alzheimer's Disease board.
"We and many others have observed that patients with dementias [that worsen with time] ... all have sleep disturbance," researcher David G. Harper, PhD, tells WebMD. "It's one of the leading reasons for institutionalization of people with dementia," as the patient is up all night, keeping the caregiver awake. Harper, the author of the study that appears in this month's Archives of General Psychiatry, is a research fellow in psychology in the department of geriatric psychiatry at McLean Hospital in Belmont, Mass., and Harvard University.
"Separating the [different causes of] dementia is really important for understanding the mechanisms of the disturbed [sleep/wake cycles] in Alzheimer's disease," expert Edward O'Malley, PhD, tells WebMD. "This [study] can really get at what the nature of that [sleep] disruption is and hopefully offer treatments."
Because sleep disturbance is the single greatest reason why caregivers feel obligated to institutionalize their loved ones with dementia, O'Malley says that this research, "can go a long way toward maintaining home care of Alzheimer's patients." O'Malley is director of the Sleep Disorders Center at Norwalk Hospital in Connecticut.
In healthy people, changes in body temperature occur throughout the day and night, they are controlled by the body clock in the brain, and they mimic activity cycles. In general, body temperature is lowest when activity levels are lowest, such as in the middle of the night, and body temperature is at its highest during periods of highest activity, such as in the middle of the day.
Harper and his colleagues studied the daily activity and body temperature cycles of 38 men who had Alzheimer's disease or another type of dementia, called frontotemporal degeneration, or FTD.
Patients with Alzheimer's disease were not only more active at night, but they also had a higher body temperature during this time period. In contrast, the daily body temperature rhythms of patients with FTD were similar to those of healthy individuals even though they were also more wakeful at night.
"Even though sleep disturbance is a common symptom of these two dementias, the cause of it appears to be entirely different," says Harper.
These results suggest that efforts to 'reset' the brain body clock -- the part of the brain that determines sleep/wake cycles, through such strategies as giving patients the sleep hormone melatonin or exposing them to bright light at certain times of the day, should work in Alzheimer's patients but not FTD patients.
Melatonin is a hormone that's produced especially at night in a gland in the brain. It is released in response to darkness and inhibited by light. It has been touted as effective treatment for jet lag and to improve longevity, among other things, though none of the claims have been conclusively proven.
Traditionally, these therapies have not always worked for Alzheimer's patients, but Harper says this is because experts did not realize how severely delayed the sleep/wake clock of Alzheimer's patients was, leading them to give the therapy at the wrong time of day.
Harper says that studies on the use of melatonin and light therapy in Alzheimer's patients should be done to see how effective they could be. During such a study, the sleep/wake cycle of each participant should be determined individually by measuring their changes in core body temperature over a 24-hour period, and the timing of therapy should be customized to each individual.
O'Malley's one concern about using these tools to reset the sleep/wake cycles of Alzheimer's patients is that some studies show that the part of the brain that is responsible for those cycles actually deteriorates during Alzheimer's disease. It's possible that at some point there will be too few cells left in that part of the brain to respond to melatonin or light therapy. An important strategy in the future, therefore, is to try to stabilize the cell loss that occurs in that part of the brain.
For news on the latest research on the body's clock and how it can relate to dementia, check out "Body Clock: How Do We Keep Time?"