Broken sleep heightens Alzheimer's risk

Aug 30, 2013

Fragmented sleep can increase one's risk of developing Alzheimer's disease, new research shows, suggesting that improvements in sleep continuity may offer a useful strategy for reducing likelihood of dementia in old age.

"An individual with high sleep fragmentation (90th percentile) had a 1.5-fold risk of developing AD as compared with someone with low sleep fragmentation (10th percentile)," says Dr. Andrew Lim, the lead author of the study and neurologist at Sunnybrook. "Previous research had suggested the possibility that sleep disruption may contribute to cognitive impairment and neurodegeneration, but a link between sleep disruption and the risk of Alzheimer's disease in older adults living in the community had never been shown."

While several studies in the past have reported associations between sleep and cognitive function in older adults, long-term community-based studies linking sleep function in older adults with the risk of developing Alzheimer's disease (AD) or the rate of cognitive decline were lacking, partly because standard sleep measurement approaches perturbed natural sleep behavior, were usually limited to a single night of testing, could only be performed in an inpatient settings, and could only be performed on relatively small groups of people because of the expense involved.

With the development of smaller, more portable devices, researchers are now able to obtain objective measures of sleep-wake behavior that are non-intrusive and do not interfere with natural sleep. They can measure rest and activity continuously 24 hours a day for days to weeks, capturing total daily sleep and providing investigators with non-invasive objective measures that overcome many of the limitations of previous investigations.

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Broken sleep heightens risk of developing Alzheimer's

Fragmented sleep can increase one's risk of developing Alzheimer's disease, new research shows, suggesting that improvements in sleep continuity may offer a useful strategy for reducing likelihood of dementia in old age.

"An individual with high sleep fragmentation (90th percentile) had a 1.5-fold risk of developing AD as compared with someone with low sleep fragmentation (10th percentile)," says Dr. Andrew Lim, the lead author of the study, neurologist at Sunnybrook Health Sciences Centre and an assistant professor at University of Toronto.  "Previous research had suggested the possibility that sleep disruption may contribute to cognitive impairment and neurodegeneration, but a link between sleep disruption and the risk of Alzheimer's disease in older adults living in the community had never been shown."

While several studies in the past have reported associations between sleep and cognitive function in older adults, long-term community-based studies linking sleep function in older adults with the risk of developing Alzheimer's disease (AD) or the rate of cognitive decline were lacking, partly because standard sleep measurement approaches perturbed natural sleep behavior, were usually limited to a single night of testing, could only be performed in an inpatient settings, and could only be performed on relatively small groups of people because of the expense involved.

With the development of smaller, more portable devices, researchers are now able to obtain objective measures of sleep-wake behavior that are non-intrusive and do not interfere with natural sleep.  They can measure rest and activity continuously 24 hours a day for days to weeks, capturing total daily sleep and providing investigators with non-invasive objective measures that overcome many of the limitations of previous investigations.

The researchers reviewed data from 737 older adults without dementia participating in the Rush Memory and Aging Project.  Sleep fragmentation was quantified from up to 10 consecutive days of monitoring in participants own homes, and the participants underwent annual evaluation over a follow-up period of up to six years, which included 19 neuropsychological tests to identify the development of AD and to assess the rate of cognitive decline.  97 individuals developed AD, and a higher level of sleep fragmentation was associated with an increased risk of AD.

This study was funded by the Canadian Institutes of Health Research (CIHR) and the National Institutes of Health (NIH), and was published in the July 2013 issue of the journal SLEEP.

Collaborators on this work included Dr. Matthew Kowgier (University of Toronto), Dr. Lei Yu (Rush University), Dr. Aron Buchman (Rush University), and Dr. David Bennett (Rush University).

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Nadia Norcia Radovini
Sunnybrook Health Sciences Centre
416.480.4040

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