(NEWSER) – A lack of shut-eye may not just leave you feeling groggy—it could seriously injure your brain. A new study of mice has found 25% of brain cells died off after prolonged sleep loss, meant to duplicate night shifts or long hours at the office—the first evidence of its kind and a scary find if it applies to humans. "We now have evidence that sleep loss can lead to irreversible injury," a researcher told the BBC, noting that when the mice lost a little sleep, they were protected by an energizing protein, but brain cells began to die off when sleep loss became a habit. "This suggests to us that we are going to have to look very carefully in humans."

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