The average person spends roughly 33% of their life sleeping. By the time you’re 50, you’ve spent roughly 146,000 hours asleep—enough to watch the original 1984 Terminator movie 81,869 times (or maybe squeeze in one run of The Lord of the Rings, extended edition).
Yet despite the massive chunk of our lives we dedicate to sleep, we don’t tend to pay much attention to what happens during sleep, possibly because we’re, well, asleep. Most of us are well acquainted with what happens when we don’t get enough sleep, though, and it isn’t pretty.
Sleep deprivation causes more than just unsightly bags under our eyes. According to the National Highway Traffic Safety Administration, driver fatigue is responsible for 100,000 motor vehicle accidents and 1,500 deaths a year, and the consequences of sleep deprivation aren’t restricted to our roads.
When an explosion that released around 400 times more radioactive material than the Hiroshima atomic bomb ripped through the Chernobyl nuclear power plant, engineers had been working for over 13 hours. When the Challenger space shuttle violently exploded just seconds after the January 1986 launch, killing all seven passengers, some of the managers had only had two hours of sleep before starting work at one in the morning. Are you seeing a pattern here?
While sleep deprivation was by no means the only factor involved in these tragedies, it’s still clear that it can have serious consequences.
Sleep and our 20,000 little biological clocks
The first mechanical clock was invented in the 14th century, but our bodies have been mysteriously keeping time since long before that.
We owe our (somewhat) reliable sleep cycles to an area within our brains called the suprachiasmatic nucleus (SCN), which we commonly refer to as the “biological clock”.
The SCN is a region made up of a mere 20,000 neurons within the hypothalamus, just above where the optic nerves cross. It plays a role in temperature and hormone regulation, sending signals to our pineal glands to regulate production of the drowsiness hormone melatonin.
More incredibly, the cells that make up the SCN all individually operate on a 24-hour time frame. You can take a cell out, isolate it in a dish, and record a 24-hour oscillation in electrical activity.
Humans have evolved such that these oscillations are synchronized with the Earth’s 24-hour rotation. When light hits our eyes, signals are sent along the optic nerve, which communicates the light intensity to the SCN.
The scientifically documented record for the longest time awake without stimulants was earned in 1947 by Randy Gardner from California, aged 17 years old, who stayed awake for a ridiculous 264.4 hours (11 days). For most of us, though, it takes significantly less time than that for the effects of sleep deprivation to rear their ugly heads.
Grumpiness, irritability, and a tendency to order double espressos can kick in after only a few hours of lost sleep, while a single day without sleep can lead to the impairment of the brain’s visual and sensory processing systems. This, combined with lessened motor control, is why lack of sleep makes us feel generally “spaced out” and clumsy.
It is also why sleep deprivation can result in horrible things like accidently putting salt instead of sugar into your fifth cup of coffee. It’s a little bit like being drunk—quite literally.
24 hours of sleep deprivation is equal to the cognitive impairment of somebody with a blood alcohol level of 0.1%, higher than the legal driving limit in the United States, Australia, Japan, Germany, Canada, the United Kingdom, Zimbabwe, China, Argentina, Brazil, and almost everywhere else. You get the drift—being sleepy is dangerous. Tell that to your boss when you’re late for work after sleeping in.
Staying awake beyond 24 hours can make our minds play serious tricks on us. Our brains start to experience sensory overload. Unable to correctly filter and interpret the incoming noise, smells, and lights, people begin to hallucinate and experience episodes of paranoia.
The hippocampus, prefrontal cortex, and parietal lobes involved in memory processing within the brain start to act up, encoding memories wrong, leading to false or even lost memories.
The temporal lobe, which plays a role in language processing, becomes less active, leading to slurred speech. Staying awake this long is a handy way to connect with your inner psycho; two of the three voices in your head may be telling you to sleep.
While it’s more dramatic to discuss the effects of staying awake for days on end, similar effects occur when sleep debt accumulates over time.
While we’re awake, our cells release a chemical called adenosine that builds up in the brain, making us feel increasingly drowsy the longer we stay awake. It’s part of a “sleep pressure” system that regulates our need for sleep.
After a good night’s sleep, adenosine is depleted and the cycle restarts, but after a poor night’s sleep, not all of the “sleep pressure” is cleared, and we’re in sleep debt. While caffeine can temporarily block the brain’s adenosine receptors, eventually you simply need to catch up on sleep.
Beyond just the general cognitive dysfunction, chronic sleep deprivation caused by increasing sleep debt also hinders immune system function and puts you at a higher risk of heart disease, depression, diabetes, and obesity. Plus, it’s just a plain old miserable experience.
Lack of sleep can literally kill
Studies performed on rats, the unluckiest creatures alive, have shown that sleep deprivation can result in the ultimate negative side effect: death. After being kept on a small disk above water, upon which they couldn’t sleep because they’d fall off and drown, all chronically sleep-deprived rats eventually died.
Speaking of torture, sleep deprivation has been extensively used as a torture method, including at Guantanamo Bay. The US military considered sleep deprivation a “humane” way of interrogation up until as recently as 2009.
Unfortunately for them, using sleep deprivation as a torture method is unlikely to get the desired results. While it may break a prisoner down, a sleep-deprived person is prone to memory loss and confusion and can experience hallucinations, making it highly improbable they’re even capable of telling an accurate version of the truth.
We’ve all experienced sleep deprivation, whether due to having a newborn baby, being overworked, or as a result of pulling an all-nighter to finish an assignment you’d known about for weeks. Sleep is the third of life we spend the least time thinking about, but our bodies are biologically programmed to need it.
You need to sleep just like you need to eat, breathe, and watch Netflix, so get comfy and get enough sleep. Your life could depend on it.