The Guardian

London:

Cut sleep out and things rapidly begin to go downhill. One of the first signs that someone is suffering from sleep loss is that they start to become moody and irritable. The brain, perhaps surprisingly, tends to be the only organ affected by sleep loss.

“There’s very little evidence that the body fails at all if you go without sleep,” says Professor Jim Horne, director of the Sleep Research Centre at Loughborough University, England. “Provided you get adequate nutrition and physical rest, all of the organs from the neck down can cope fine.”

Not so the brain, however. It’s one organ that really can’t cope without sleep. Specifically, it’s a region of the brain called the cerebral cortex that suffers the most. The cerebral cortex is arguably what makes us human. “Without that, you become an automaton, a robot,” says Horne.

And that is exactly what the acutely sleep-deprived turn into. The transition to human robot can kick in after just two days without sleep. “You end up just staring at things because you don’t know what to look at next.” Gradually, other symptoms begin to appear, like being easily distracted and unable to take part in conversations.

“If you are in a conversation (with a sleep deprived person), they will most likely have stilted speech and speak in a monotone and not about anything at all interesting,’’ adds Horne.

Sleep-deprived people have increased appetites, become shaky, get headaches and, mysteriously, get more horny. After three days without sleep, hallucinations can kick in.

The longest scientifically documented case of sleep deprivation was provided by an

American, Randy Gardner, in 1964 who in an attempt to set a world record, stayed awake for 11 days.

Four days in, he had a hallucination in which a street sign turned into a person, an episode quickly followed by a delusion where he though he was a famous black footballer. The hallucinations are due to what sleep scientists call dream intrusion.

Just how long a human can go without sleep is hard to judge, except to say that it is likely to be much longer than Gardner managed. After sleeping off his 11-day awake-athon, he showed no signs of long-term physical or mental damage.

Horne says the idea that people kept awake for days will eventually go mad and start beating each other is nonsense. “What’s far more likely is they’ll just sit around and finally conk out.”

Pushed to the absolute limit, however, the human body will ultimately succumb to sleep loss, although it would likely take more than 30 days of constant wakefulness. Rather than the brain burning out, sleep deprivation would ultimately become fatal because of the stress it causes.

“If something was keeping you awake that long, you would have such a stress reaction that your immune system would probably collapse,” says Horne.

The immune system is constantly fighting small battles with microbes all over the body. When it collapses, the battle and the war are lost. “You would die of wholesale, massive infections. It would be like an extreme form of blood poisoning.”