A little embellished
A horror story with headlines like "Even one sleepless night can lead to Alzheimer's disease" spread through the world and Russian media with the filing of not only yellow newspapers, but also from embellished retellings of a publication in the popular science publication New Scientist with a more correct headline "One bad night's sleep may increase levels of Alzheimer's protein" (One sleepless night can increase Alzheimer's protein levels). The British National Health Service (NHS) has explained in detail what is wrong here.
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The study that caused such a fuss was conducted on only 20 volunteers and lasted for two days. None of the participants suffered from Alzheimer's disease. The study consisted of two stages: on the first night, the subjects were allowed to sleep at night as long as they wanted, and on the second they were not allowed to sleep all night. After each night, the amount of beta–amyloid in their brain was determined using positron emission tomography and florbetaben, a radiopharmaceutical drug for the diagnosis of Alzheimer's disease. It is known that this protein accumulates, forms plaques that damage neurons and cause Alzheimer's disease. But the correlation between the amount of beta-amyloid itself, not plaques, and the risk of Alzheimer's disease has not been confirmed in any study. Especially if we are talking about a short-term increase in beta–amyloid - and this is what the study describes.
According to the results of the study, after a sleepless night, the level of beta-amyloid in the brain was on average 5% higher than after a full sleep. This figure does not prove that beta-amyloid continues to accumulate further – there is no data for a longer observation.
We do not deny the benefits of full sleep – it is certainly necessary for physical and mental health. But to take seriously the conclusions about the risk of Alzheimer's disease, obtained in a two-day small study, is at least frivolous.
How did it all start?
The study was conducted by employees of the National Institutes of Health (USA) and the Yale School of Medicine (USA). The results were published in the authoritative American journal PNAS (Proceedings of the National Academy of Sciences). British media with unreasonably disturbing headlines distorted the meaning of the study.
If the risk of Alzheimer's depended on sleepless nights, then the incidence would be simply incredible. Who among us is not sinful and has not spent at least one night out of bed, chatting with friends or watching a favorite TV series? For some people, for example, young parents, sleepless nights generally become the norm of existence for several years.
How was the study conducted?
It was an experimental study: scientists identified changes before and after the intervention.
In order to draw any conclusions, the design of the study must be different. The duration of observation should be increased in order to be able to assess further fluctuations in the amount of beta-amyloid in the brain. It would be worth complicating the experiment: for example, adding a few more full nights to the study after one sleepless night. It is likely that after them, the beta-amyloid indicators return to normal.
A randomized controlled trial (RCT) would be ideal, when participants who are approximately identical in gender and age are randomly assigned to two groups (experimental and control) and differences in indicators between them are observed depending on the amount of sleep.
But even such a study design would not give reliable results, because a larger–scale work is needed to identify risk factors - a cohort study. It is held with the participation of a large number of people (hundreds or thousands) and lasts for a long time (more than one year). In the course of the study, at certain time intervals, it is necessary to conduct regular assessments of the amount of sleep and the level of beta-amyloid in the brain, and then try to prove or disprove a certain connection between them.
Who participated in the study?
20 healthy volunteers aged 22 to 72 years (average age 40 years). The study did not include those who had any physical or mental abnormalities, including bad habits. Excluded those who were constantly taking medications, recently received sedatives and painkillers.
Each study participant underwent a brain scan after a night of full sleep and after a sleepless night. A full-fledged sleep was considered from 10 pm to 7 am. The nurse monitored every hour whether the subject was sleeping or not.
A sleepless night is staying awake from 8 a.m. until 13-30 the next day. The nurse also monitored the participants every hour. Participants were banned from drinking any caffeinated beverages. After midnight, eating was prohibited until morning.
In addition to determining the level of beta-amyloid in the brain, a questionnaire was conducted in which participants were asked to answer questions about cases of Alzheimer's disease among blood relatives.
Research results
The authors compared the brain scans after a full sleep and a sleepless night. They found a difference in the amount of beta-amyloid: in the second case, it was 5% higher. But this is an average indicator, if we compare individual people, the difference fluctuated greatly. It did not depend on gender, age or heredity. The mood after a sleepless night was generally worse. The more the beta-amyloid level changed, the more broken the person felt.
How did the researchers interpret the results?
The authors called the results of the study "preliminary evidence" of insufficient sleep as a risk factor for increasing the amount of beta-amyloid in the brain. They wrote that improving the quality of sleep may be one way to prevent Alzheimer's disease.
The authors admit that it is impossible to determine whether the accumulated beta-amyloid is capable of forming insoluble plaques that damage brain tissue, or whether it is washed out of the body.
Conclusions
The study has many limitations. Its value is to help in the formation of a hypothesis that needs to be tested in higher–quality and larger works. No clinical conclusions should be made based on it. Moreover, we are talking about attributing lack of sleep to the category of risk factors for Alzheimer's disease.
A significant drawback of the study is the number and selection of participants. There were only 20 of them, none of them had signs of age-related dementia. In addition, based on the results of only two measurements, it is impossible to determine the relationship of a slight increase in beta-amyloid with a lack of full sleep.
We don't know:
- how does the level of beta-amyloid change from day to day;
- does beta-amyloid accumulate after repeated sleepless nights;
- will any of the participants develop Alzheimer's disease or not;
- is there a link between beta-amyloid and other factors;
- can a short-term increase in the amount of beta-amyloid really increase the risk of Alzheimer's disease.
It is also worth noting that sleep deprivation in the study was quite extreme: participants were awake for about 31 hours. In ordinary life, insomnia rarely drags on for such a long period.
Alzheimer's disease, despite the prevalence and interest of researchers, unfortunately, remains insufficiently studied. This study also does not answer the question about the possible causes of the disease.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru According to NHS materials: Don't lose sleep over reports that one bad night can spark dementia.