12 July 2017

Disturbed sleep causes an increase of amyloid beta in the brain, which is a protein that has been linked to Alzheimer's disease. After several sleepless nights, the amount of the protein tau rises as well, which is another protein associated with brain damage caused by Alzheimer's and other neurological conditions. A single night of poor sleep is sufficient to cause a detectable effect on the brain already.

One feature of Alzheimer's disease are deposits and plaques formed from the proteins amyloid beta and tau. These deposits are formed over a long period of time, presumably ten to twenty years. The damages caused by these plaques become apparent in the form of cognitive problems. Both proteins actually occur naturally in the brain: the amount of amyloid beta rises during the day and typically decreases during sleep. Accordingly, loss of sleep causes a rise in beta amyloid in the brain. In this way, chronic sleep shortages can play a role Alzheimer's disease.
Previous research at Radboudumc and the Donders Institute showed that a single sleepless night led to a detectable increase of amyloid beta in the brain. The researchers suspected quickly that this might be caused by disturbances in deep sleep phases specifically. In order to test this hypothesis directly, researchers at Radboudumc, Donders, Washington University School of Medicine, and Stanford University conducted another sleep experiment with 17 healthy volunteers. The participants went to take a night's rest in a sleep laboratory, while their brain waves were being measured.

A Single Bad Night Causes Rises in Amyloid Beta already

On the morning after the experiment, all participants gave some of their cerebrospinal fluid for testing. A single night of disturbed sleep caused the amount of amyloid beta to rise by a stunning ten percent. The amount of tau was not different after a single bad night, although it was increased in people who had also slept poorly during the preceding week. This confirms that tau deposits build up more slowly than deposits of amyloid beta.
The researchers emphasize that a single or several bad nights do not imply an increased risk for Alzheimer's disease. Another night of good sleep will probably let the proteins return to their normal levels. The fact that poor sleep increases the levels of proteins that are associated with Alzheimer's, does not immediately reveal whether good sleep shields against Alzheimer's disease, explains Jurgen Claassen: "We cannot say for certain whether there is a causal relationship between sleep quality and Alzheimer's disease. But decent sleep has other proven health benefits and there are good and effective treatments, even non-pharmaceutical, for sleep disorders. Anticipating further research, I'll dare to recommend everyone to mind getting a good night's rest."

Jurgen Claassen

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