Researchers examined fruit flies' brain behavior and activity.

We know that a good night's sleep has a positive impact on our physical and mental health, and can reduce the risk of heart disease, depression, and stress, but a new study from researchers at Northwestern University has found that a deep sleep also has the ability to clear waste thanks to an ancient, restorative power. "Waste clearance could be important, in general, for maintaining brain health or for preventing neurogenerative disease," said Dr. Ravi Allada, senior author of the study. "Waste clearance may occur during wake and sleep but is substantially enhanced during deep sleep."

woman sleeping
Credit: Getty / mapodile

In the study, researchers followed the relationship between sleep patterns and waste in fruit flies' brains. Although the size of their brains are significantly smaller than humans', researchers have found that their sleep-wake cycles are remarkably similar to ours. The team examined proboscis extension sleep, a deep-sleep stage in fruit flies, which is similar to deep, slow-wave sleep in humans, and found that the flies repeatedly extend and retract their proboscis (or snout). "This pumping motion moves fluids possibly to the fly version of the kidneys," Allada said. "Our study shows that this facilitates waste clearance and aids in injury recovery."

Overall, the study further supports the theory that maintaining a consistent wake-up time and bedtime can help you to sleep better night after night. Health professionals and sleep experts say that most adults should aim to sleep seven to eight hours each night. "Our finding that deep sleep serves a role in waste clearance in the fruit fly indicates that waste clearance is an evolutionary conserved core function of sleep," the paper's coauthors write. "This suggests that waste clearance may have been a function of sleep in the common ancestor of flies and humans."

A 2013 study from the National Institutes of Health used mice in a similar experiment to determine how toxins flow through the brain during sleep. "These findings have significant implications for treating 'dirty brain' diseases like Alzheimer's," said Dr. Maiken Nedergaard of the University of Rochester Medical Center.


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