Dementia: A good night's sleep keeps the brain fit

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MunichToo little sleep damages the brain - this is nothing new. But now US scientists have identified which structural changes could be responsible for it.

Subjects in the scanner

Professor Kristine Yaffe from the University of California and her colleagues investigated the relationship between sleep habits and brain structure. To find out whether poor or poor sleep can really lead to cognitive decline and dementia, they asked over 640 participants, ages 37 to 52, about their sleep: how many hours they slept per night and whether they woke up frequently. About 50 percent said that they slept less than seven hours - the short sleepers. Only five percent rested for more than eight hours - the late risers.

Five years later, the researchers pushed their subjects into the magnetic resonance imaging (MRI) scanner and scanned their heads.

Illuminated brain

In both short sleepers and late sleepers, the scientists found so-called hyperintensities in the white matter of the brain, which consists of the long nerve endings. Hyperintensities show up as white spots on MRI images because these areas are where the neurons are excessively active. This indicates pathological changes that occur both with age, but can also point to neurodegenerative diseases such as multiple sclerosis or dementia. The changes were only visible in the parietal areas of the brain, which are responsible for recognizing stimuli, for example - but not in other regions.

Rapid movement of molecules

In addition, the researchers discovered another typical sign of rapid cognitive decline in short sleepers and test persons with many sleep interruptions: an increased mean diffusivity in several brain regions. This means that the water molecules in the affected areas of the tissue moved faster. This was not the case for participants who slept longer or better.

Hen or egg?

From the results it cannot be clearly determined whether the poor sleep actually disrupts the brain substance and thus promotes dementia. Conversely, damage to the white matter could also disrupt sleep.

It also remains to be seen whether too much sleep could damage the brain. Since so few participants were late risers, the results are not statistically significant in this regard.

When sleeping becomes difficult

People spend about a third of their lives sleeping. It is only when you have problems falling asleep or staying asleep that you realize how important it is to get a good night's sleep. According to the Munich Sleep Medicine Center, an average of 15 percent of all adults in Germany suffer from sleep disorders that require treatment. Sleep problems can have physical or psychological causes. (vv)

Source: Yaffe, K. et al. 2014. Summary of the poster presentation. American Academy of Neurology Annual Meeting.

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