What you didn’t know about sleep: The 5 most surprising facts

We all do it night by night and, in the end, spend around a third of our entire life doing it: we’re talking about sleep. With all that time spent on it, you would think that we know exactly what is going on in our bodies. But for most of us, sleep is still a big mystery. Find out about some of the most surprising sleep facts:

Sleep Fact Nr. 1

Every night, your sleep cycle passes from light sleep to deep sleep to REM sleep and then repeats throughout the night. Each of these sleep stages are vital to your health, and every phase plays a unique role in maintaining it.

During the phases of deep sleep, your body does what we would expect it to do when sleeping: the muscles relax, your heart rate, breathing and body temperature drop. But when you enter the REM stage of sleep (REM = Rapid Eye Movement, also known as the “dream phase”) it starts to get interesting (and, admittedly, a little freaky): as your brain becomes more active, dreams start to occur. To protect the body from hurting itself, full skeletal muscle atonia takes places, meaning that all skeletal muscles become immobilized, except for the eyes. During that time, your muscles are not tense as you would expect, but completely limp.

REM atonia usually goes unnoticed as a natural process when moving from one sleep phase to the next. However, around 40% of all people can consciously experience a case of sleep paralysis at least once in their life. In those cases, people would experience the paralysis just before falling asleep or right after waking up. 

Sleep Fact Nr. 2

In the year 2020/2021, almost 1 billion kgs of coffee beans were consumed worldwide. Backed by that number, it’s safe to say that coffee is one of the most consumed beverages all around the world. What makes it so wonderful is that after drinking it, you feel energised, awake and ready to take on the world. 

So if you’re a true coffee lover, you might want to skip the next part, because we would hate to spoil it for you.

Because unfortunately, coffee is not the miraculous little helper we believe it to be. While drinking a delicious Latte Macchiato or Espresso might make you FEEL more awake, all it really does is masking your need to sleep. In your brain, a chemical called adenosine is responsible for your desire to sleep (together with the circadian rhythm, but we leave this factor out for the moment). It accumulates throughout the day and determines when you feel sleepy. By drinking coffee and taking in caffeine, you are muting the sleep signal by blocking the receptors normally reserved for the sleep chemical. Approximately thirty minutes after the first sip, you will feel awake and alert. The problem about it: caffeine wears off. And during the whole time you felt on top of the world, the sleepiness chemical adenosine kept building up and will now hit you with even more sleepiness; you experience a caffeine crash (it's basically all the sleepiness you felt a few hours ago PLUS the extra adenosine that has accumulated since drinking your coffee). The only way out is a nap – or more coffee.

Sleep Fact Nr. 3

We don’t sleep the way nature intended. This might sound like a bold statement, but hear us out: Most modern cultures have cultivated a monophasic sleep pattern, meaning that they get all their „needed“ sleep in one bout during the night. However, there is clear evidence that shows nature would have you sleep in what is called a biphasic sleep pattern, e.g. sleeping a longer period at night and getting a shorter nap (30-60 minutes) in the afternoon.

Exhibit A: Every human being, no matter their location or cultural influence, experiences a dip in alertness mid-afternoon. This brief change from high wakefulness to low-level alertness, called the post-prandial alertness dip, is usually accompanied by drowsiness and the strong urge for a nap.

Exhibit B: Tribes that are mostly untouched by modern society display the perfect example of biphasic sleep, getting their night-time sleep from sometime after sunset to just before sunrise, complementing it with an afternoon nap.

For a long time, mostly southern countries still implemented the biphasic sleep pattern with a „siesta“ in the afternoon. How beneficial this short nap is to your health showed an extensive study executed by Harvard University’s School of Public Health around the millennium years: They monitored around 23’000 Greeks across a 6 year period, during a time when the Greek government tried to remove the typical „siesta“ from its system. Its results show that for those who stopped taking a siesta during the six years, the risk of dying from heart disease increased by 37% compared to those still following the practice of taking an afternoon nap.

Sleep Fact Nr. 4

Not getting enough sleep for a few nights might not seem like a big deal to you; you might tell yourself that you can always catch up the missed hours over the weekend. However, studies have shown that already a single night of too little can wipe out 70% of the protective cells circulating the immune system.

But it's not just your immune system that takes a toll from sleep deprivation; there is no aspect of health that can escape its consequences. There is two medical conditions in particular that are closely linked to not getting enough sleep: cardiovascular diseases (such as heart attacks) and obesity. 

Multiple studies have shown that short sleep is associated with a 35-45% greater risk of fatal and nonfatal coronary heart disease when sleeping less than six hours a night over a longer period, compared to the regular seven to eight hours of sleep. This is especially important during midlife: adults 45 or older who sleep fewer than six hours a night are 200% more likely to have a heart attack or stroke during their lifetime.

When it comes to weight gain and obesity, studies show different results for the likelihood of becoming obese due to a lack of sleep; it ranges from 15 to 40% for participants that slept five hours or less compared to those who slept seven hours a night. The connection between the two, however, cannot be denied. For children, it is even more distinct than it is for adults. 

Sleep Fact Nr. 5

Would you deem yourself fit to do your job or drive a car after drinking 2-4 glasses of wine? No? We wouldn’t, either. On the other hand, you would probably drive into work after a sleepless night, thinking that well, it cannot be that bad.

Truth is: being tired has the same effect as being drunk. After 17hrs of no sleep you loose 50% of your reaction time and your level of concentration is the same as after 2 glasses of wine. Add another 7 hours of no sleep and your comprehending and communication skills, productivity and concentration will be as impaired as with 4 glasses of wine.

Not getting enough sleep impairs a lot of our brain functions such as speech, memory, impulsiveness and decision-making. The one brain function, however, that suffers the most from sleep deprivation is concentration. And it’s not just all-nighters we’re talking. A study of the University of Pennsylvania has shown that participants getting “only” 6 hours of sleep for ten days showed the same drop in concentration as someone that hadn’t been sleeping for 24 hours straight.

Behind the wheel, sleep deprivation gets particularly dangerous: a study done by the AAA Foundation in Washington DC shows that when operating a vehicle on less than 5 hours of sleep, your risk of a car crash multiplies by 3, and it grows exponentially the less you sleep.

But sleep deprivation isn’t just dangerous behind the wheel; going to work on too little sleep can have disastrous ramifications – quite literally. For example, sleepiness was a clear contributing factor not only in the Chernobyl nuclear accident but also the Challenger Space Shuttle accident in 1986.

If you want to learn more about how and why we sleep, we highly recommend the international beststeller "Why We Sleep" by Matthew Walker.