It took two days for the effects of not getting a single second of sleep to begin to surface in 17-year-old Randy Gardner.

First, it was his sight and sense of touch. His eyes started struggling to focus and his hands weren’t as easily identifying objects.

But with all the bravado of a typical teenage boy, Randy would continue to stay awake for an additional nine days.

He was intent on smashing the world record for the longest time spent without sleep. And at 2am on January 8, 1964, he did exactly that, beating the current one by four hours. In total, he shunned sleep for 264.4 hours – or 11 days and 24 minutes. And he did it without any stimulants other than the odd can of Coca-Cola.

Randy shot to global fame, his experiment shedding rare light on what happens to our bodies when we stop sleeping.

And it all began because two teenage boys, who were a little bored during Christmas break, decided they wanted to win a local science competition.

Randy and his friend Bruce McCallister knew they had to do something really big to get the top prize in the Greater San Diego Science Fair. After all, this was a big city. That’s when they came up with their idea to test the effects of sleeplessness.

They flipped a coin and it was decided: Randy would be the guinea pig.

“We were idiots, you know young idiots,” Bruce McCallister told the BBC in January. “I stayed awake with him to monitor him… and after three nights of sleeplessness myself I woke up tipped against the wall writing notes on the wall itself.”

They enlisted a third friend, Joe Marciano, and he and Bruce began to operate in shifts so that Randy was never awake alone.

Their little team continued to swell. When Marciano joined, a sleep researcher from Stanford University, William Dement, caught wind of the experiment in a local newspaper and got involved – much to the relief of Randy’s parents who were terrified for their eldest son.

Randy’s early strategy was simply to stay away from any beds and to keep standing as much as possible. At first, it was easy.

But two days in, his sight began to blur slightly and by day three, nausea kicked in.

“I noticed that in the morning I was really nauseous, and that’s when I stumbled on eating citrus for some reason. Tangerines or oranges seemed to take the nausea away,” Randy told NPR in 2017.

It was around this time that he also became moody and uncoordinated. His senses of taste, smell and hearing started to wane.

And the longer he was awake, the more his cognitive abilities began to slip. Randy recalls starting to feel like he had "early Alzheimer's".

"It was crazy, where you couldn't remember things, it was almost like an early Alzheimer's thing brought on by lack of sleep," he said.

As the days wore on, Randy had to step up his tricks for staying awake. He'd play basketball and go bowling. But nights were the worst. With nothing to do, keeping his eyes open was torturous.

But at last, he reached his goal of 264 hours. And it's at this point where there is some contention. Two professionals who worked closely with him did not agree on just how much of an impact extreme sleep deprivation had on the teen.

Psychiatric researcher Lt Cmdr John J Ross, who monitored Randy's health, said the behavioural and coginitive effects were severe, including problems with concentration, short-term memory, hallucinations (on day five he thought a room in front of him was a forest) and paranoia (on day 10 he thought a radio show host was making him look foolish). Ross' findings on day 11 are reported in the Psychiatric Times.

"Expressionless appearance, speech slurred and without intonation; had to be encouraged to talk to get him to respond at all. His attention span was very short and his mental abilities were diminished. In a serial sevens test, where the respondent starts with the number 100 and proceeds downward by subtracting seven each time, Gardner got back to 65 (only five subtractions) and then stopped. When asked why he had stopped he claimed that he couldn't remember what he was supposed to be doing."

Meanwhile, Dement always insisted the effects were little more than some mood changes and basic sensory impairments. He would use the example that on day 10, he took Randy to a restaurant and they played pinball, which the teenager even won.

It was also noted that when Randy began to sleep again, there were no obvious long-term psychological or physical consequences.

Immediately after the experiement ended, Randy was whisked away to a naval hospital so scientists could attach electrodes to his head and monitor his brain.

“So he sleeps for 14 hours – we’re not surprised – [and] he wakes up, in fact, because he has to go to the bathroom. His first night his percentage of REM state sleep, which was at that point associated with dream-state sleep – it isn’t anymore – skyrocketed. Then the next night it dropped in percentage points until finally days later it returned to normal," Dement said.

“And then he got up and went to high school… it was amazing."

Bruce told the BBC the tests from hospital found Randy's brain had been "catnapping" during the 11-day experiment, meaning parts of it would be asleep to restore while others would be awake.

But while Randy didn't appear to show any negative effects, he said he later suffered from insomnia for years. He is convinced his teenage experiment was responsible.

"I was awful to be around. Everything upset me. It was like a continuation of what I did 50 years ago," he told NPR last year.

While Dement and Ross disagreed when it came to the results of Randy's project, what is known is that sleep deprivation can have serious ill-effects. These include mood changes, weight-gain, heightened blood pressure, illness and in some rare cases, premature death.

Even seemingly small shifts to our sleep patterns can have devastating impacts. In 2014, a US study found losing an hour of sleep with daylight savings time increased the risk of having a heart attack by 25 per cent. But getting an extra hour? The risk falls by a one-fifth.

Of course, in the end, Randy and his two friends won the science fair. More importantly, he will also forever own the world record. After snatching the title, the Guinness Book of World Records cut the category and refused to certify any further attempts to beat it because of the associated health dangers.

And to this day, 54 years later, Randy's science project remains one of the most documented accounts of a human intentionally going without sleep.