A preliminary study by researchers at Uppsala University found that when we are deprived of a single night's sleep, the presence of one of the main biomarkers of Alzheimer's disease - the level of tau protein , increases in the blood.
The tau proteins are present in neurons (constituting a family of six isoform proteins), but in too high quantities, they can accumulate and generate clusters. Buildings of tau protein are visible in the brains of people with Alzheimer's disease. This characteristic can begin decades before the onset of symptoms of the disease.
Previous studies in older adults have suggested that sleep deprivation can increase tau levels in cerebrospinal fluid. Head trauma can also increase tau levels in the blood.
"Many of us experience sleep deprivation at some point in our lives due to jet lag, a sleepless night to complete a project, teamwork, nights at work or inconsistent hours," said study author Jonathan Cedernaes of the University of Uppsala in Sweden. “Our exploratory study shows that even in young and healthy individuals, a missed night's sleep causes a slight increase in the level of tau in the blood. This suggests that over time, similar types of sleep disturbance could potentially have detrimental effects.” The results were published in the medical journal Neurology .
A preliminary study with interesting results
The study looked at 15 healthy men, of normal weight and on average 22 years old. They all reported that they regularly get seven to nine hours of quality sleep a night.The tests took place in two phases . For each phase, the men were observed on a strict meal and activity program for two days and two nights, in a sleep clinic. Blood samples were taken in the evening and in the morning.
For the first phase , the participants were able to sleep normally during the two nights. For the second phase , they could only benefit from a full night's sleep (only the first day), followed by a night of sleep deprivation.
During the night of sleep deprivation, the lights were on while the participants sat in their beds to play games, watch movies or chat.
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| Illustration summarizing the course of the study and its conclusions. Credits: Uppsala University |
17% increase in tau protein
The researchers found that men showed an average 17% increase in the rate of tau in their blood after only one night of sleep deprivation, compared to an average increase of 2% in the rate of tau after a good night's sleep.The researchers also looked at four other biomarkers associated with Alzheimer's disease, but no level change was observed between a normal night's sleep and a sleepless night.
"It is important to note that if the accumulation of tau in the brain is not good, in the context of sleep loss, we do not know what higher levels of tau in the blood represent," a said Cedernaes.
“When the neurons are active, the release of tau in the brain is increased. Higher blood levels may mean that these tau proteins are eliminated from the brain, or reflect an overall increase in the concentration of tau levels in the brain. More studies are needed to explore this question further, as well as to determine how long these changes in tau levels last. It will also be a question of understanding whether the changes in blood tau reflect a mechanism by which recurrent exposure to restricted, disturbed or irregular sleep can increase the risk of dementia,” he adds.
These studies could provide key information on whether sleep-targeting interventions should start at an early age to reduce the risk of developing dementia or Alzheimer's disease.
The main limitation of the study is of course the limited sample (few individuals tested). In addition, it relates only to young healthy men. As a result, the results may differ for women or the elderly.
| Bibliography: Effects of acute sleep loss on diurnal plasma dynamics of CNS health biomarkers in young men Christian Benedict, Kaj Blennow, Henrik Zetterberg, Jonathan Cedernaes First published January 8, 2020, DOI: https://doi.org/10.1212/WNL.0000000000008866 |
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