Health experts have been concerned about our sleep-deprived ways for some time, but insights about the role sleep plays in overall health have brought an urgency to the message, reports TIME Magazine.

“We all want to push the system, to get the most out of our lives, and sleep gets in the way,” says Dr. Sigrid Veasey, a leading sleep researcher and a professor of medicine at Perelman School of Medicine at the University of Pennsylvania. “But we need to know how far we can really push that system and get away with it.”

Veasey is learning that brain cells that don’t get their needed break every night are like overworked employees on consecutive double shifts–eventually, they collapse. Working with mice, she found that neurons that fire constantly to keep the brain alert spew out toxic free radicals as a by-product of making energy. During sleep, they produce antioxidants that mop up these potential poisons. But even after short periods of sleep loss, “the cells are working hard but cannot make enough antioxidants, so they progressively build up free radicals and some of the neurons die off.” Once those brain cells are gone, they’re gone for good.