Over the past 20 years, our understanding of sleep has improved dramatically, and it turns out that getting consistent sleep every night is more important and non-negotiable than we could have ever imagined.

When you don’t get enough sleep, an overwhelming number of bad things happen.

The most extreme? Death.

If you don’t sleep, you will eventually die.

The longest time a human has been recorded staying awake while being monitored closely is 11 days and 25 minutes; this record was set in 1964 by Randy Gardner, a 17-year-old high school student in San Diego, California. But due to the health risks, the Guinness World Records stopped acknowledging the record, as well as any subsequent attempts to beat the record in 2004, when the listing for sleep deprivation and wakefulness records disappeared.

In 2012, a 26-year-old man from China attempted to watch every game of the Euro 2012, a soccer championship series in Europe. He died after 11 days without sleep. He was also drinking and smoking.

People with the rare sleep disorder, fatal familial insomnia, die within 12 to 18 months after much suffering. In lab settings, sleep-deprived rats die in 11 to 17 days.

Sleep deprivation is a form of torture.

Israel’s former prime minister, Menachem Begin, who was once tortured by the KGB in Russia, wrote in his autobiography, White Nights: The Story of a Prisoner in Russia that torturers were able to get prisoners to sign anything, not by offering freedom, but simply depriving them of sleep, and then offering an uninterrupted block of sleep. On this, Menachem writes:

In the head of the interrogated prisoner a haze begins to form. His spirit is wearied to death, his legs are unsteady, and he has one sole desire: to sleep, to sleep just a little, not to get up, to lie, to rest, to forget…Anyone who has experienced this desire knows that not even hunger or thirst are comparable with it…I came across prisoners who signed what they were ordered to sign, only to get what their interrogator promised them. He did not promise them their liberty. He promised them—if they signed—uninterrupted sleep.

Even minor sleep deprivation is extremely harmful.

Obviously, being tortured or going for a world record is on the extreme end of the spectrum of sleep deprivation. Still, many studies over the past 20 years have conclusively found that habitually sleeping under 7 hours a night is deadly.

Here are some studies and findings to back this up: (Also see my review of Matthew Walker’s book, Why We Sleep.)

Shifting the clock forward one hour for Daylight Savings = 24% increase in heart attacks the following day

In the spring, when we adjust our clocks forward for Daylight Savings, there is a 24% increase in heart attacks the following day, as people get one hour less of sleep. This is not a coincidence, because when we shift our clocks back one hour in the autumn and get an extra hour of sleep, there is a 21% reduction in heart attacks the following day.

This amazing statistic shows how important sleep is, and how even just one hour can mean the difference between life and death.

70% reduction in Natural Killer Cells after sleeping 4 hours for just one night.

Here’s a particularly disturbing example: just sleeping 4 hours for one night (many people sleep 4 hours most of the work week) leads to a horrifying 70% reduction in cancer-fighting cells.

In your body, you have things called Natural Killer Cells (NK Cells.) They are like the Special Forces of your immune system. If your NK Cells come across a cancer cell, they will punch a hole in the malignant tumor’s outer surface, and inject a protein that will destroy it.

However, after just a single night of 4 hours of sleep, the number of natural killer cells in your body decline by a harrowing 70%, compared to when you get a full 8 hours of sleep.

That is what Dr. Michael Irwin discovered at the University of California when he studied healthy young men, and subjected them to a single night of 4 hours of sleep, after allowing them to get 8 hours of sleep the previous night.

Increased risk for Alzheimer’s disease

There is a causal link between sleep deprivation and Alzheimer’s disease. Early in his career, Matthew Walker discovered that patients with Alzheimer’s disease displayed a signature brain pattern when asleep. Originally a dementia researcher, Walker began studying sleep to find out more. What he thought would be a two year detour ended up taking him twenty years.

How is sleep deprivation linked to Alzheimer’s disease? When we are awake, we accumulate toxic proteins in our brain, one of which is called beta amyloid. (This is why Walker refers to wakefulness as “low-level brain damage.”) When we’re asleep, our brain cleans out the toxic protein buildup. But when we don’t get proper sleep, this toxic protein buildup accumulates, interfering with brain functions, which seems to play a key role in the eventual development of Alzheimer’s. Much research is still being conducted, but the link between sleep deprivation and Alzheimer’s is pretty clear at this stage.

40% increased risk of developing cancer when sleeping 6 hours or less.

The extreme reduction in NK cells after being sleep deprived (which I mentioned above) is probably the reason why multiple studies found that sleeping 6 hours or less is associated with a 40 percent increased risk of developing cancer.

These studies include a European study of ~25,000 people, and a study that tracked over 75,000 women across an 11-year period.

3X more likely to catch a cold when sleeping less than 7 hours a night

If inadequate sleep can increase the rate of cancer and heart attacks, it shouldn’t be surprising that it increases the chances of catching a cold.

A Carnegie Mellon University study showed that sleeping less than 7 hours a night increases your vulnerability to colds three-fold.

4X stroke risk

Researcher, Megan Ruiter, said the following at the 2012 SLEEP conference: “People sleeping less than six hours had four times increased risk of experiencing these stroke symptoms compared to their normal weight counterparts that were getting seven to eight hours.”

Gene Distortion

Your DNA is the code that contains the instructions and programming for every cell in your body. When you don’t get enough sleep, that genetic code becomes distorted and unreadable, like a scratched DVD, which leads to health problems that can manifest themselves in a seemingly infinite number of ways. Patients who slept for 6 hours per night for a week had 711 genes that were distorted.

Lower testosterone, smaller testicles

Men have traditionally flexed their machismo by displaying willingness to partake in harmful, dangerous activities, and foregoing comfort and safety nets to “prove their toughness.” If there are men who find it unmanly to use an umbrella in the rain, there are men who think succumbing to the desire for sleep is unmanly.

But it’s now known that men who sleep to 5 hours a night have smaller testicles, lower testosterone levels (that of someone 10 years older), and lower fertility. According to sleep expert, Matthew Walker PhD, “Men who sleep 5 hours a night have significantly smaller testicles than those who sleep 7 hours or more.” Women aren’t exempt; female reproductive health also suffers from less-than-optimal sleep.

Athletics

300% decrease in reaction time

One all-nighter has been shown to decrease reaction times by 300%. Brain scans showed that people simply failed to react, as if their brains had momentarily flat-lined. This momentary inability of the brain to respond is called micro-sleep and is the cause of many tragic car accidents and deaths. Indeed, micro-sleeping behind the wheel of a vehicle weighing over one ton and moving at 70 miles per hour is tragedy waiting to happen.

More likely to get in a car accident

A school in Wyoming changed the start of the school day from 7:35am to 8:55am. As a result, the number of 16 to 18-year-olds involved in car crashes were reduced by 70%. To put that in perspective, the invention of ABS “only” reduced car crashes 20-25%, and it was deemed a revolution. In other words, if drivers on the roads were always properly rested, it would reduce accidents more effectively than the invention of ABS.

6 hours of sleep = 30% decrease in stamina

A study showed that time to exhaustion decreased by 30%.

After 20 hours of being awake, you are as impaired as a drunk person.

Most people are awake 16 hours a day. Stay up 4 hours later than that, and you are as good as drunk. When you go out partying late, your decision-making abilities are at its worst, as it combines sleep deprivation with alcohol.

Decreased ability to perspire and cool the body

Humans are capable of performing unbelievable feats of endurance, such as the endurance hunting conducted by the San People, where a tribesman essentially chases down a much quicker animal until it collapses from exhaustion.

The reason this extraordinary feat is even possible is because humans can perspire to cool themselves, whereas many animals, including the kudu shown in the video, can’t. When you don’t sleep properly, your ability to sweat and regulate your body’s temperature is impaired.

You eat worse

When you’re sleep deprived, you naturally eat bigger portions or unhealthy food, and have a preference for high-carb, high-calorie foods.

Lower pain threshold

Scientists in Norway found a link between insomnia and low pain threshold.

Mental

You are 60% more emotional when you don’t get enough sleep

You are 60% more emotional when you don’t get sleep. The worst part is, you don’t even realize it.

Brain scans revealed that after sleep deprivation, the brain’s emotional centers were 60%+ more reactive, according to a 2007 study from University of California, Berkeley, and Harvard Medical School.

When you don’t sleep, the prefrontal cortex (the CEO of your brain, responsible for logical, rational thought) stops working properly, and the amygdala (responsible for emotion) becomes more active. This means you become “unable to place events into a broader or considered context.”

Matthew Walker wrote in his bestselling 2017 book, Why We Sleep, that brain scan analysis during the study showed that the “amygdala—a key hot spot for triggering strong emotions such as anger and range, and linked to the fight-or-flight response—showed well over a 60 percent amplification in emotional reactivity in the participants who were sleep-deprived. In contrast, the brain scans of those individuals who were given a full night’s sleep evinced a controlled, modest degree of reactivity in the amygdala, despite viewing the very same images. It was as though, without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity. We produce unmetered, inappropriate emotional reactions, and are unable to place events into a broader or considered context.”

At the time of the study, Walker also noted:

“It’s almost as though, without sleep, the brain had reverted back to more primitive patterns of activity, in that it was unable to put emotional experiences into context and produce controlled, appropriate responses.”

Delusions and Hallucinations

When you don’t get enough sleep, your body activates its fight-or-flight response, which puts you in a state of hyper arousal, delaying the negative impact of sleep deprivation. It makes you euphoric, which puts a positive spin on your predicament, essentially a delusion that is masking how taxing the sleep deprivation is to your system.

It is also well known that losing enough sleep will lead to hallucinations, as was the case with Peter Tripp, a radio personality from the 1950’s who stayed awake on the air for 201 hours. After his stunt, he had lasting delusions for some time that he was an imposter of himself.

40% reduction in ability to form memories and learn; 60% drop in problem-solving ability.

When you pull an all-nighter, your ability to learn and form new memories decreases by 40%, compared to when you get 8 hours of sleep.

That’s according to a study conducted by sleep expert, Matthew Walker. Walker and his team conducted a study where people were divided into two groups: the sleep group and the sleep deprivation group. People in the sleep group slept 8 hours, and those in the sleep deprivation group were kept up all night under supervision without caffeine or naps. The next day, everyone was put into MRI scans, and then tasked with learning a list of facts while their brain activity was monitored. Then they were tested to see how effectively they learned. Long story short, the group that pulled the all-nighter did 40% worse.

Why did that happen? What’s the mechanism behind that 40% decline in learning ability? Well, the hippocampus is like a memory card. When you don’t sleep, it’s as if the memory card suddenly malfunctions, and no longer allows you to store new memories. When you don’t get enough sleep, your brain fails to place your experiences and thoughts into the hippocampus. Thus, you will lose the memory.

Why is this relevant? 40% is the difference between a student passing and failing a test, considering that an perfect A+ minus 40 points is an F. 40% is also the difference between a businessperson remembering 10 facts told to them by a client, or forgetting 6 and failing to deliver according to their client’s expectations.

How does sleep help you learn?

In general, sleep acts as a save button to the things you learn. During sleep, things go into the hippocampus. If you want to know what it’s like to not have a functioning hippocampus, watch the movie Memento.

Learning is synonymous with memory. If you’re good at something, it’s because you have a great memory for it, whether it’s muscle memory, or episodic memory. Chess grandmasters keep thousands of chess games stored in their memory and can make lightning-fast decisions that mesmerize laymen. Experienced boxers memorize patterns of behavior from opponents, and what kind of punches are possible for an opponent to throw from a certain position. Musicians remember the exact configuration that their body or instrument needs to be in to hit the right note. Expertise is basically someone saying, “I’ve done this correctly, many times before, and I remember.”

How losing sleep affects you socially

Losing sleep for even just one night makes you significantly more emotional and volatile. If you’re more emotional, you’re bound to make mistakes socially: you perceive slights where there aren’t, cause scenes when you shouldn’t, get into fights when they’re unnecessary, and embarrass yourself in all sorts of ways. When you fail socially, you have less friends, which means less opportunities and support from others.

Less Attractive to Others

You are perceived as less attractive when you don’t get enough sleep. People who don’t get sleep are subjectively rated as less attractive than when they are getting sleep. There are numerous studies that have been done on this; here’s one that was done in the UK with 30 women.

On the left, the subject got 8 hours of sleep. On the right, the subject got only 6 hours of sleep (for one night):

That’s just ONE NIGHT, imagine a week! Actually, you don’t have to. In another study organized by London’s Sleep School, participants like Sarah Chalmers slept 6 hours a night for an entire week. The difference in her appearance before and after the experiment is dramatic:

What 6 hours of sleep for a week looks like

Chalmer’s pores doubled in size due to increased oil secretion and her face reddened by 50%, among other things. She reported feeling “permanently hungry”, and irritable.

According to Dr. Sturnham, “Sleep loss causes the body to release too little human growth hormone, which promotes the repair of skin cells. What you are seeing is your skin’s inability to heal itself. Your face has become redder because it has an increased sensitivity to the bacteria generated by the rise in cortisol.”

Sleep deprivation also leads to broken capillaries.

What 4 hours of sleep for 3 nights in a row looks like

Here’s another one: an 18-year-old named Chloe de Garis conducted a self-experiment where she only got four hours of sleep for three nights straight. Aside from the annotations, the photos were not altered:

Chloe’s makeup artist said, “Over the course of just three days, Chloe had lost her glow…her skin has deteriorated…it was bumpy to touch and very tight…quite a few blemishes and her eyes are dark.”

Her dermatologist said, “I can see increased redness and breakouts showing on Chloe’s skin…face looks dry in places, and less plump.”

People don’t like you as much when you’re sleep deprived

As if being groggy and cranky weren’t bad enough consequences for losing sleep, a 2017 study in the Royal Society Open Science Journal showed that people literally don’t like you as much when they sense that you’re sleep deprived. They’re less likely to interact with you, and their bodies actually become repelled by the sight of you, setting off disease-avoidance mechanisms when in the presence of a sleep-deprived person.

When humans see an unhealthy face, it activates disease-avoidance mechanisms. Therefore, people are less likely to interact with someone who looks sleep-deprived.

In the study—conducted at Sweden’s Karolinska Institute—researchers had 25 male and female students sleep well (8 hours) for two nights in a row. Then, they took pictures of the students without makeup. Next, the students were restricted to 4 hours of sleep for two consecutive nights. Another set of pictures were then taken. Researchers presented the pictures to 122 strangers who were told to rate each student’s image in terms of attractiveness, health, sleepiness, and trustworthiness. For sleep deprived students, their 4-hour sleep pictures were rated worse in attractiveness, health, and sleepiness compared to their 8-hour pictures. The judges also expressed that they would be less inclined to socialize with the sleep-deprived individuals.

Hope you found this interesting!

I will add more information here as I find it, so bookmark this page. You can also add facts you know that I’ve missed in the comments below. Thank you!