MODERN society is increasingly ill equipped to provide our brains with the requisite cleaning time. The figures are stark. Some 80 percent of working adults suffer to some extent from sleep deprivation. According to the National Sleep Foundation, adults should sleep seven to nine hours. On average, we’re getting one to two hours less sleep a night than we did 50 to 100 years ago and 38 minutes less on weeknights than we did as little as 10 years ago. Between 50 and 70 million people in the United States suffer from some form of chronic sleep disorder. When our sleep is disturbed, whatever the cause, our cleaning system breaks down. At the University of Pennsylvania’s Center for Sleep and Circadian Neurobiology, Sigrid Veasey has been focusing on precisely how restless nights disturb the brain’s normal metabolism. What happens to our cognitive function when the trash piles up?

At the extreme end, the result could be the acceleration of neurodegenerative diseases like Alzheimer’s and Parkinson’s. While we don’t know whether sleep loss causes the disease, or the disease itself leads to sleep loss — what Dr. Veasey calls a “classic chicken-and-egg” problem — we do know that the two are closely connected. Along with the sleep disturbances that characterize neurodegenerative diseases, there is a buildup of the types of proteins that the glymphatic system normally clears out during regular sleep, like beta-amyloids and tau, both associated with Alzheimer’s and other types of dementia.

“To me,” says Dr. Veasey, “that’s the most compelling part of the Nedergaard research. That the clearance for these is dramatically reduced from prolonged wakefulness.” If we don’t sleep well, we may be allowing the very things that cause neural degeneration to pile up unchecked.

Even at the relatively more benign end — the all-nighter or the extra-stressful week when you caught only a few hours a night — sleep deprivation, as everyone who has experienced it knows, impedes our ability to concentrate, to pay attention to our environment and to analyze information creatively. “When we’re sleep-deprived, we can’t integrate or put together facts,” as Dr. Veasey puts it.

But there is a difference between the kind of fleeting sleep loss we sometimes experience and the chronic deprivation that comes from shift work, insomnia and the like. In one set of studies, soon to be published in The Journal of Neuroscience, the Veasey lab found that while our brains can recover quite readily from short-term sleep loss, chronic prolonged wakefulness and sleep disruption stresses the brain’s metabolism. The result is the degeneration of key neurons involved in alertness and proper cortical function and a buildup of proteins associated with aging and neural degeneration.

It’s like the difference between a snowstorm’s disrupting a single day of trash pickup and a prolonged strike. No longer quite as easy to fix, and even when the strike is over, there’s likely to be some stray debris floating around for quite some time yet. “Recovery from sleep loss is slower than we’d thought,” Dr. Veasey notes. “We used to think that after a bit of recovery sleep, you should be fine. But this work shows you’re not.”

If you put her own research together with the findings from the Nedergaard lab, Dr. Veasey says, it “very clearly shows that there’s impaired clearance in the awake brain. We’re really starting to realize that when we skip sleep, we may be doing irreparable damage to the brain, prematurely aging it or setting it up for heightened vulnerability to other insults.”