A peaceful night of sleep clears the mind — literally, according to neuroscientist Jeff Iliff.
In a recent TEDMED talk, the University of Rochester researcher says that healthy brains use the downtime of sleep to basically clean house.
“When the brain is awake and is at its most busy, it puts off clearing away the waste from the spaces between its cells until later,” says Iliff. “Then when it goes to sleep and doesn’t have to be as busy, it shifts into a kind of cleaning mode.”
Iliff was referencing a study that he and his colleagues from the University of Rochester Medical Center published last year. They discovered that the sleeping brains of mice wash away debris accumulated during a day’s worth of action-packed thinking and doing — the very same debris that clogs the brain of an Alzheimer’s patient.
Every cell in our body feeds on nutrients and produces metabolic waste as a byproduct. It's a bit like "engines producing exhaust," says naturopathic doctor Angele Besner.
"This cellular byproduct becomes toxic to cells if it’s allowed to accumulate and hang round too long," Besner wrote on her blog. "Brain cells are delicate and especially vulnerable to this kind of damage."
When we enter the dream world of sleep, explains Iliff, brain cells shrink, opening up the space between them and allowing cerebrospinal fluid to wash away these toxic substances. “It’s like a dishwasher,” explains study lead author and neurosurgeon Dr. Maiken Nedergaard in an interview with NPR.
But not every brain is able to clean itself.
“In patients with Alzheimer’s disease, [the waste product] amyloid beta builds up and aggregates in the spaces between the brain’s cells instead of being cleared away like it’s supposed to be,” explains Iliff.
Indeed, amyloid beta buildup is a longtime hallmark of the disease, explains Alzheimer’s Foundation of America, dating back to an autopsy of the first-identified Alzheimer’s patient in 1906.
Many neurological disorders — Alzheimer's, yes, but also dementia and stroke — are linked to sleep disorders, Nedergaard tells Science, which noted that "the study suggests that lack of sleep could have a causal role, by allowing the byproducts to build up and cause brain damage."
"This could open a lot of debate for shift workers, who work during the nighttime,” Nedergaard told Science. "You probably develop damage if you don’t get your sleep."