Every night since humans first evolved, we have made what might be considered a baffling, dangerous mistake. Despite the once-prevalent threat of being eaten by predators, and the loss of valuable time for gathering food, accumulating wealth, or having sex, we go to sleep. Scientists have long speculated and argued about why we devote roughly a third of our lives to sleep, but with little concrete data to support any particular theory. Now, new evidence has refreshed a long-held hypothesis: During sleep, the brain cleans itself.
Many neurological diseases—from Alzheimer's disease to stroke and dementia—are associated with sleep disturbances, Nedergaard notes. 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 predicts. "You probably develop damage if you don’t get your sleep."
