After examining previous studies in sleep-deprived mice, many of which were conducted by Dr. Veasey, the researchers found that when animals were kept awake just a few hours longer than usual each day, two key areas of the brain were particularly affected: the locus coeruleus, which manages feelings of alertness and arousal, and the hippocampus, which plays an important role in memory formation and learning. These regions, which are central to maintaining conscious experience in humans, slowed animal production of antioxidants, which protect neurons from unstable molecules that, like exhaust fumes, are constantly produced by functioning cells. When antioxidant levels are low, these molecules can build up and attack the brain from within by breaking down proteins, fats and DNA.
“Alertness in the brain, even under normal circumstances, carries with it penalties,” said Dr. Fernandez. “But if you stay up too long, the system gets overloaded. At some point you can no longer beat a dead horse. If you ask your cells to stay active 30 percent longer each day, cells will die.
In the brains of mice, sleep deprivation led to cell death after a few days of sleep restriction—a much lower threshold for brain damage than previously thought. It also caused inflammation in the prefrontal cortex and increased levels of tau and amyloid proteins, which have been linked to neurodegenerative diseases such as Alzheimer’s and Parkinson’s, in the locus coeruleus and hippocampus.
After a full year of regular sleep, the previously sleep-deprived mice still suffered from neural damage and brain inflammation. for dr Veasey and Mr. Zamore, this indicated that the effect was long-lasting and perhaps permanent.
Still, many scientists said the new research shouldn’t be cause for panic. “It’s possible that sleep deprivation damages the brains of rats and mice, but that doesn’t mean you should fret about not getting enough sleep,” said Jerome Siegel, a sleep scientist at the University of California at Los Angeles, who this did not contribute to the review.
dr Siegel noted that neural injury occurs in stages, and the extent of sleep deprivation’s impact on the human brain is still largely unknown. He also expressed concern that over-concern about the long-term effects of sleep deprivation could lead people to seek more sleep unnecessarily and with medication.