For a long time, scientists believed that the brain gets rid of toxins and harmful particles during sleep, but a new study claims that the opposite may be true.
The study revealed that activity may be more beneficial for "cleaning" the brain.
A team from the Dementia Research Institute at Imperial College London used a fluorescent dye to study the brains of mice, tracking how quickly the dye moved from one area of the brain to another before it was eventually eliminated.
The researchers discovered that dye clearance and movement decreased significantly during sleep and under anesthesia.
The analysis revealed that the dye clearance decreased by about 30% in sleeping mice, as well as 50% in mice that were under anesthesia, compared to mice that remained awake.
Study co-author Nick Franks, professor of biophysics and anesthesia at Imperial College London, said: “Research has focused heavily on the idea of detoxification as one of the main reasons we sleep, and we were of course very surprised to see the opposite in our results.”
The researchers also said that the size of toxic particles may affect how quickly some toxins move through the brain, as some compounds are eliminated through different systems.
Franks added: “Until now, we do not know what these conditions are that slow down the removal of molecules from the brain. The next step in our research will be to try to understand why this happens.”
Professor Bill Wisden, one of the leaders of the study, said: “There are many theories about why we sleep, and although we have shown that detoxification may not be a major cause, the importance of sleep cannot be disputed. Interrupted sleep is a common symptom that people suffer from.” "In people with dementia, however, we still do not know whether this is a consequence or a driving factor for the development of the disease. Perhaps good sleep helps reduce the risk of developing dementia for reasons other than detoxification."
He added: "The other aspect of our study is that we showed that brain clearance is highly efficient during the awake state. In general, being awake, active, and exercising may lead to the brain cleaning of toxins more efficiently."
The findings, although they need to be confirmed in humans, cast doubt on the long-held belief that sleep removes toxins through the glymphatic system (the mechanism that flushes toxins from the brain).
It is noteworthy that previous studies indicated that sleep is important for the prevention of dementia, as toxic proteins are removed from the brain.
The results were published in the journal Nature Neuroscience.
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