Sleep loss damages the fatty insulation protecting the nerve cells in our brain, according to a paper published in the journal Proceedings of the National Academy of Sciences. The research also explains why we often feel slow and groggy after a bad night’s sleep.

Most of us will experience sleep loss at one time or another and suffer the consequences of tiredness and slower reactions the next day. The biological mechanisms for these are not well understood and often attributed to tired or overworked neurons. Researchers led by scientists at the University of Camerino in Italy thought there might be other factors at play, so they decided to investigate.