New findings published in the journal Brain may help explain why poor sleep has been linked to the development of dementias such as Alzheimer’s. Previous studies have demonstrated that the risk of cognitive problems increases with poor sleep, but they were not able to explain why disrupted sleep caused damage to brains.

To better understand the link, researchers studied 17 healthy adults ages 35 to 65 who were given an activity monitor to measure their nightly sleep for at least five nights. The participants then spent a night at the School of Medicine in a specially designed sleep room. Half of them were randomly assigned to have their sleep interrupted by a series of beeps through headphones as soon as their brain signals settled into the slow-wave pattern that characterises deep sleep.  The beeps would continue until the participants’ brain patterns showed they had entered shallower sleep. The other half slept normally.

The next morning, those whose sleep was disrupted reported feeling tired and unrefreshed. The participants also underwent a spinal tap to measure the levels of amyloid beta and tau in their brain fluid and spinal cord. A month later, the participants came back again, but the uninterrupted sleep group had their sleep disrupted, while the interrupted sleep group was allowed to sleep normally.

Analysis of the participants’ amyloid beta and tau levels showed a 10 percent increase in amyloid beta levels after a single night of interrupted sleep, but no increase in tau levels. Increased tau levels were found in participants whose activity monitors recorded poor sleep for a week prior to the spinal tap.

While the study was not designed to determine whether better quality or more sleep can reduce the risk of Alzheimer’s, neither can hurt.

Paper: “Slow wave sleep disruption increases cerebrospinal fluid amyloid-β levels”
Reprinted from materials provided by Washington University in St. Louis.

szeptember 21, 2017