A new study from the University of Pennsylvania is showing that ignoring sleep for work or other activities can do more than just make you feel tired:  it can actually kill brain cells.

This is the first sleep study showing permanent brain damage from lack of sleep.  Previous studies had only shown a drop in cognitive abilities, strength and focus without focusing on long term damage.

Dr. Sigrid Veasey, the study’s author, said that neuroscientists knew certain neurons in the brain that did not sleep as long as the person was awake.  They focused on those cells because they believed fatigue in those cells impacted long-term brain health.

“This gave us an indication that maybe [the cells] needed their rest,” she says. “We hypothesized that the cells that were going to be the most likely to get injured would be some of the cells that are active during wakefulness.”

The study showed a loss of as much as 30 percent of neurons in the studied group that was kept sleepless for the longest period of time.

“You can push the system a little bit, but you can’t push it too hard and for too long or you’ll have irreversible consequences,” she says.