Sleep and Waste Control

The American Association for the Advancement of Science (AAAS) recently announced the award for the 2014 Newcomb Cleveland Prize that goes to an outstanding paper published in their flagship journal, Science. AAAS is the nation’s premier scientific society, and their journals publish reports of significant discoveries in all fields of science from astrophysics to zoology. The 2014 award went to a paper describing a remarkable discovery about the purpose of sleep, a question that has confounded researchers for decades. A team of scientists at the University of Rochester Medical Center discovered that the glymphatic system, the brain’s unique system for clearing out metabolic wastes, is engaged more during sleep than during wake periods. The restorative function of sleep may depend on how efficiently toxins are cleared from brain cells during sleep.

These results are instrumental in understanding how sleep is related to neurodegenerative diseases such as Alzheimer’s Disease. In Alzheimer’s patients, excess amounts of the peptide amyloid-beta are thought to cause buildup of plaques that result in neuronal loss and brain atrophy. Inadequate sleep results in less complete flushing of these toxins. These processes are consistent with observations that patients with Alzheimer’s and other neurological diseases associated with dementia often have comorbid sleep disorders.

Source: By National Institutes of Health [Public domain], via Wikimedia Commons

This recent discovery has implications for treatment of these neurogenerative diseases, and it also provides one more explanation for why sleep is beneficial for all persons. It also may account for some of the individual differences in need for sleep, as the glymphatic system may operate slower, or less efficiently in some persons than others.

Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., ... & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373-377.