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14-07-2013 | Neurology | Article

Fragmented sleep possible harbinger of cognitive decline


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medwireNews: Fragmented sleep in older adults may increase their rate of cognitive decline and risk for Alzheimer’s disease (AD), actigraphy-based study findings indicate.

The results showed that for every 1 standard deviation increase in sleep fragmentation, measured as the probability of having an arousal in a 15-second period, the risk for developing AD up to 6 years later increased 1.22-fold.

“These findings were not accounted for by variation in total daily rest time, total physical activity, the presence of chronic medical conditions, or the use of common medications which can affect sleep,” the researchers, led by Andrew Lim (University of Toronto, Ontario, Canada), point out.

They believe that improving sleep continuity could help reduce the burden of cognitive decline and dementia in old age.

The team used actigraphs to measure sleep fragmentation in 737 adults, aged an average of 81.6 years, over a relatively long period of up to 10 consecutive days. The more frequently bouts of sleep or rest were interrupted by arousals, the greater the degree of sleep fragmentation.

Higher levels of sleep fragmentation were significantly associated with the risk for AD, which developed in 97 individuals over an average follow up of 3 years, and was diagnosed based on 19 neuropsychologic tests.

Indeed, individuals with high sleep fragmentation in the 90th percentile had a 1.5-fold higher risk for developing AD than individuals with low sleep fragmentation in the 10th percentile.

To eliminate the possibility of AD misdiagnosis, the researchers also assessed the effects of sleep fragmentation on cognitive decline. This showed that a 0.01 unit increase in sleep fragmentation was associated with a 22% increase in the annual rate of cognitive decline relative to the average rate in the cohort.

“Given the magnitude of both cognitive impairment and sleep disturbances in older adults, determining whether sleep fragmentation is associated with incident AD and cognitive decline in old age has important public health implications,” the researchers comment in Sleep.

“This work demonstrates an association,” concludes the team. “This raises the possibility that interventions to decrease sleep fragmentation may offer a potentially useful strategy for reducing the risk of AD and slowing cognitive decline in older individuals.”

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Lucy Piper, Senior medwireNews Reporter

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