We spend a third of our lives sleeping. It is one of our most basic needs. Studies have shown that adequate sleep promotes immune function, healing and much more. Sleeping is such an innate drive that people will actually choose it over eating.

A good night’s sleep is one of life’s sweetest blessings. And yet, nobody knows what sleep really is–not even neuroscientists.

You’ve probably heard that we need to do it in order to stay sane, to stay alive, but beyond that, much of its exact function still remains a mystery. When people don’t get enough sleep, they begin to hallucinate and go slightly crazy. Sleep deprivation paints a very stark picture. It can result in psychotic episodes and breakdowns, pre-sleep twilight, weight loss, dementia, paranoia, and yes, even death.

If you happen to suffer from bouts of insomnia, then you know just how important it is to get some shut eye. You’ll also be able to sympathize with the subject of this bizarre medical case from 1915. He is one of the only known people to have ever survived without sleep for an extended period of time.

During the First World War, Paul Kern, a Hungarian soldier, was shot in the head. After recovering from the frontal lobe injury, he was no longer able to fall asleep or become drowsy, not even with narcotics, sedatives, or hypnotism. Doctors initially told him that he wouldn’t live very long, but they were shocked to discover they were completely wrong.

Kern thrived. Instead of sleeping, he would simply lie down and close his eyes to rest from time to time. He went on to live a healthy, abundant life and survive without sleep for 40 years, until his death in 1955.

So, how long can humans stay awake? The answer remains unclear.

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