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Study finds that losing a night of sleep may increase Alzheimer’s biomarker

A preliminary study has revealed that when deprived of one night of sleep, young, healthy men had higher levels of tau in their blood. Tau is a biomarker for Alzheimer’s disease.

Tau is a protein found in neurons, and can form into tangles, which then accumulate in the brains of people with Alzheimer’s disease. This process can begin and tangles can start to develop in the brain years before symptoms of the disease will appear. Previous studies have suggested that sleep deprivation in older adults can increase the level of tau in the cerebral spinal fluid. Head trauma can also increase concentrations of tau in the blood.

“Many of us experience sleep deprivation at some point in our lives due to jet lag, pulling an all-nighter to complete a project, or even doing shift work, working overnights or inconsistent hours,” said study author Jonathan Cedernaes, MD, PhD, from Uppsala University in Sweden. “Our exploratory study shows that even in young, healthy individuals, missing one night of sleep increases the level of tau in blood suggesting that over time, such sleep deprivation could possibly have detrimental effects.”

The participants in the study were 15 healthy, normal-weight men with an average age of 22, who all reported that they regularly got seven to nine hours of good sleep per night.

The study was split into two phases – in each phase, the men were observed under a strict meal and activity schedule in a sleep clinic for two days and nights. The scientists collected blood samples in the evening and again in the morning. In one phase, the participants were able to get a good night of sleep for both nights. In the other phase, the participants were allowed to get a good night of sleep for the first night, which was followed by a night of sleep deprivation. During sleep deprivation, the lights were kept on and participants sat up in bed playing games, watching movies, or talking.  

The researchers discovered that the participants had an average 17% increase in tau levels in their blood after a night of sleep deprivation compared to an average 2% increase after a good night of sleep.

Four other biomarkers associated with Alzheimer’s were examined, but there were no changes in levels relating to sleep deprivation.

 “It’s important to note that while higher levels of tau in the brain are not good, in the context of sleep loss we do not know what higher levels of tau in blood represent” said Cedernaes. “When neurons are active, production of tau in the brain is increased. Higher levels in the blood may reflect that these tau proteins are being cleared from the brain or they may reflect elevated tau levels in the brain. Future studies are needed to investigate this further, as well as to determine how long these changes in tau last, and to determine whether changes in tau in blood reflects a mechanism by which recurrent exposure to restricted, disrupted or irregular sleep may increase the risk of dementia. Such studies could provide key insight into whether interventions targeting sleep should begin at an early age to reduce a person’s risk of developing dementia or Alzheimer’s disease.”

The main limitation of the study was its small size. In addition, it looked only at healthy young men, so the results may not be the same for women or older people.

https://n.neurology.org/content/early/2020/01/07/WNL.0000000000008866

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