Cleansing the brain of toxins and waste is more active when awake than asleep.
A study published in Nature Neuroscience reveals that the brain’s process of clearing out toxins and waste is more active when awake than asleep.
The research team measured how toxins and waste were removed from the brain by calculating the ratio of a dye moving from the brain’s ventricles to other brain areas.
The researchers reported that the dyed areas decreased 30% less during sleep and 50% less when anesthetized, indicating that the brain’s purging process is more productive when awake than when asleep or anesthetized.
Due to lack of sleep, humans often experience health issues such as decreased focus and hand-eye coordination. The study refutes the previously commonly believed hypothesis that the cause of this phenomenon is the lack of clearing out the brain due to lack of sleep.
Experts argue that there must be a specific reason why animals must sleep, even though the sleeping posture is vulnerable to attack and seems disadvantageous for survival.
They believed that tasks that cannot occur or be efficiently carried out while awake happen during sleep, with brain cleaning and memory enhancement being the representative hypotheses.
Meanwhile, experts point out that this study is an animal experiment and needs further clinical trials for validation. They also note that the results could differ if a high-molecular dye is used instead of the small-molecular dye used in this study.
Moreover, the research team induced sleep deprivation in mice before evaluating wakefulness. They added that the results could differ when sleep is not deprived, as the circadian rhythm affects brain cleaning.
Experts caution that the study’s results do not refute the hypothesis that levels of proteins associated with neural degeneration increase during periods of active neural activity, i.e., wakefulness.
They explained that proteins related to neural degeneration increase when sleep is lacking, and sleep disturbances interfere with the regulation of amyloid beta and tau proteins associated with Alzheimer’s pathology. Even if brain purifying is more active when awake, the risk of Alzheimer’s and neural degeneration is higher in a state of prolonged wakefulness, i.e., sleep deprivation. Therefore, experts suggest that even if the brain cleaning process is not more active during sleep than when awake, there may be other mechanisms by which sleep maintains brain health.
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