In December 1963, two boys thought of a bright idea for a school science project– they would stay awake for as long as possible and report back on what happens inside their sleep-deprived brains. The project ended on 8 January 1964, when 17-year-old Randy Gardner had managed to stay awake for 11 days and 25 minutes, setting a world record.

When asked by reporters who crowded the front yard of his parent’s home in San Diego how he managed the feat, Gardner answered philosophically. “It’s just mind over matter,” he said.

Gardner’s record hasn’t been broken ever since, although the Guinness Book of Records stopped certifying attempts, fearing that it would be too dangerous for people’s health. Some have even wondered: can you die from lack of sleep?

A sleep-deprived brain is a stupid brain

Whether sleep deprivation can kill is somewhat debatable. That’s because people who forgo sleep for extended periods of time may also use a lot of stimulants from the benign coffee to the more dangerous types of drugs, such as cocaine and methamphetamine. So, it can be difficult to single out a person’s cause of death in fatalities that involve sleep deprivation. Was it the countless hours without sleep that killed a person or was it the drugs? Or was it both?

In 2012, a Chinese man died after he went 11 days without sleep — almost as much as Gardner — in an attempt to watch every game in the Euro 2012 football championship. The 26-year-old man was reportedly in good health, according to The Telegraph, but he drank and smoked while watching the football.

Typically, one wouldn’t expect people to die just from lack of sleep, as long as no substances have been consumed. But that doesn’t mean that sleep deprivation is harmless.

The detrimental effects of sleep deprivation appear after just 24 hours of no sleep, such as rising stress hormone levels, which raises blood pressure.

After two days of no sleep, the body’s ability to turn glucose into energy is diminished and the immune system stops working as well as it does when fully rested. The body’s internal temperature also begins to sink.

By day three, cognitive abilities are profoundly impaired, especially short-term memory and executive functions such as paying attention and multitasking.

“I mean, it was crazy, where you couldn’t remember things, it was almost like an early Alzheimer’s thing brought on by lack of sleep,” Gardner told NPR’s Hidden Brain podcast, more than 50 years after he showed just how long you can go without sleep.

And since sleep deprivation causes parts of the brain to work together in a chaotic way, as if you had taken stimulant drugs, hallucinations can also occur as a result.

According to Matthew Walker, a neuroscientist at the University of Berkeley, even an hour of insufficient sleep can have dramatic health consequences. To illustrate his point, the neuroscientist mentions the results of the largest sleep experiments ever done, which have been performed on over 1.6 billion people — it’s called daylight saving time. In the spring, we lose an hour of sleep, a period that is associated with a 24% increase in heart attacks. In the fall, we gain an hour of sleep, which is associated with a 21% decrease in heart attacks.

In a 2018 study, Walker and colleagues also found that sleep-deprived individuals are less likely to engage with others, and are more likely to feel lonely, exhibiting symptoms similar to social anxiety. Researchers have found that loneliness is just as lethal as smoking 15 cigarettes per day and that lonely people are 50 percent more likely to die prematurely than those with healthy social relationships. However, that’s not to say that sleep deprivation summarily causes these deaths.

One cruel study from the 1980s performed by researchers at the University of Chicago, placed rats on discs above a tray of water. The rodents weren’t allowed to doze off because the rotating risc would always shove them towards the water, startling them back awake. Within a month, all the rats died, although the researchers weren’t sure why. Possibly, the stress of being awoken at least a thousand times a day broke the animals down.

However, a person that intentionally wants to stay awake for days at a time won’t be as stressed as if they were tortured to stay awake. And even if that happened, is it the stress or the sleep loss that killed the person?

While sleep deprivation may not kill you on the spot, it has been linked to a greater risk of diabetes, obesity, depression, heart conditions, and other health problems. Luckily, our bodies have pretty good defense mechanisms that help most people avoid insufficient slumber. By making us lack energy, feeling groggy, and generally miserable, the body sends a clear message: ‘please sleep!’

According to the Sleep Foundation, adults should sleep between seven to nine hours per night, while kids should clock in about 10 to 11 hours a night. However, approximately 35 percent of adults in the United States do not get enough sleep. 

If your job or family situation makes it impossible to sleep enough, you can try napping. A 2017 study found that only a half an hour nap can restore your protein and hormone levels to normal.

Bottom line: sleep deprivation won’t kill you, but it will make you suffer greatly.