The human brain is one of the great scientific mysteries of the universe, with questions on the nature of consciousness and cures for illnesses that plague this organ alone perplexing researchers nearly as much as the deepest areas of the Earth’s oceans or the far reaches of space. It’s enough to keep you awake at night, which turns out might be putting you at risk for some of those brain diseases in the first place.
Advancement in medical technology to study the brain has been relatively recent. For Alzheimer’s, the most common cause of dementia and sixth highest cause of death in the United States, the triggers of nerve cell damage and degeneration were discovered about 30 years ago to be proteins known as beta-amyloid and tau; as these proteins clump or tangle together in the brain, they block the transmission of nutrients and electrical impulses. But little has been understood since as to how a healthy brain disposes of this protein waste, and how this process could be connected to reversing the damage done by neurodegenerative diseases.
New research published in an upcoming issue of Scientific American magazine reveals that a previously undiscovered system exists for clearing the brain of proteins and other wastes—and in an important revelation for our over-exhausted society, this system is most active during sleep.
The authors, Dr. Maiken Nedergaard and Dr. Steven A. Goldman, set out to study how the brain disposes of its waste products. Until recently, it was believed that—despite the fact that the brain consumes 20 to 25% of the body’s total energy—the brain and spinal cord were somehow not connected to the lymphatic system that processes the rest of the body’s waste, and that the brain might in fact somehow recycle the waste it produces. But what the researchers found was a new system they named the glymphatic system, in which the heart’s pumping of blood through the arteries in the brain also pushes large amounts of cerebrospinal fluid into perivascular spaces throughout the cranial cavity. Using a specific type of glial cell called an astrocyte as a conduit, the cerebrospinal fluid travels through the brain tissue, picking up discarded proteins, then exits the brain through the perivascular space that surrounds veins that drain the brain and goes on to enter the lymph system and the general bloodstream.
In bad news for those who brag about how sleep-deprived they are, the research showed that this process of clearing waste proteins out of the brain was tied heavily to sleep patterns. When brain scans were conducted on mice, they showed that when the mice were asleep, the space between brain cells through which the glymphatic fluid flows increased by up to 60% and the removal of beta-amyloid proteins more than doubled. The article authors point to studies that show Alzheimer’s patients reported sleep disturbances long before other symptoms became apparent, as well as to additional studies that show those who report poor sleep patterns in middle age are at higher risk of cognitive decline later in life. They speculate that poor sleep patterns are not only a side effect of cognitive decline, but also an exacerbating factor in the progress of neurodegenerative diseases.
In other words: get some damn sleep already.
The Scientific American article will be publicly available Tuesday, March 1st. Previously, Dr. Maiken Nedergaard presented on the ideas behind this research in 2014 at the University of Rochester Medical Center.
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