By Tracy Brighten
Research revealing that sleep cleanses the brain of toxins has been awarded a top prize in the advancement of science
Scientists have long sought to establish the function of sleep, proposing that there must be a more essential function than the storing and consolidation of memories, considering an animal’s vulnerability during the sleep state. Sleep is also known to have a restorative effect on the human brain, and lack of sleep impairs brain function, but how does this occur?
Research that has revealed the main function of sleep as clearing toxins from the brain was recently awarded the 2014 Newcomb Cleveland Prize of the American Association for the Advancement of Science. This annual award recognises outstanding research published in the journal Science.
Led by Maiken Nedergaard, researchers at the University of Rochester’s Medical Center, in collaboration with Oregon Health and Science University, and New York University, have contributed significantly to the understanding of neurodegenerative diseases like Alzheimer’s that are linked to a build-up of cellular waste products such as the protein amyloid-beta.
Their paper, “Sleep Drives Metabolite Clearance from the Adult Brain”, suggests that during the wakeful state when the brain is processing information, there is insufficient energy to remove waste that accumulates from activity, so the cleansing occurs during sleep. Using in vivo two-photon imaging, researchers observed the influx of cerebral spinal fluid (CSF) into the cortex of awake, anaesthetised, and sleeping mice.
Researchers found that the glymphatic system, the brain’s own waste removal system identified in previous research by Nedergaard and colleagues, is more active during sleep. Cells in the brain contract, increasing the interstitial space by more than 60 percent and boosting the flow of CSF between cells to cleanse the brain of amyloid-beta and other toxins.
In light of this ground-breaking discovery, regular sleep patterns recommended by the National Sleep Foundation – 7 to 9 hours for adults aged 18 to 64 and 7 to 8 hours for over 65s – not only improve memory and mental health as other studies have shown, but may also reduce the risk of neurological diseases.
First published on Science Nutshell February 24, 2015
Xie, L., Kang, H., Xu, O., Chen, M. J., Liao, Y., Thiyagarajan, M., O’Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., & Nedergaard, M. (2013). Sleep Drives Metabolite Clearance from the Adult Brain. Science, 342 (6156), 373-377.
University of Rochester Medical Center Newsroom (2015, February). Study that Shows How Brain Cleans Itself While We Sleep Honored by AAAS. Retrieved from: http://www.urmc.rochester.edu/news/story/index.cfm?id=4254
University of Rochester Medical Center Newsroom (2013, October). To Sleep, Perchance to Clean. http://www.urmc.rochester.edu/news/story/index.cfm?id=3956
Pinol, N. D. (2015, February). Paper on Sleep’s Restorative Effects Wins 2014 AAAS Newcomb Cleveland Prize. http://www.aaas.org/news/paper-sleeps-restorative-effects-wins-2014-aaas-newcomb-cleveland-prize
National Sleep Foundation. (2015, February 2). Expert panel recommends new sleep durations. ScienceDaily. Retrieved February 24, 2015 from www.sciencedaily.com/releases/2015/02/150202123716.htm