Effects of Sleep Deprivation on Cognition and Health

1. Degraded Attention

When you don't get enough sleep, attention is often the first thing to go.

You might remember sitting in class having stayed up way too late studying the night before. No matter how hard you try, it feels impossible to pay attention. Your eyelids weigh a hundred pounds, your head sinks into your hands or onto your desk, and without even realizing it, you zone out and miss almost everything that your teacher says.

Sleep deprivation impairs something called selective attention. This is your ability to focus on one specific thing instead of paying equal attention to everything in the world around you. In class, for example, you use your selective attention to listen to your teacher. There are tons of other stimuli that are occurring at the same time, like students taking notes or people walking outside the window. A well-functioning brain can tune those things out, but sleep deprivation can make concentration seem impossible.

This discovery comes from Willamette University. Their researchers examined the selective attention of two groups of people: one got a full night's sleep while the other was sleep-deprived. Both groups were instructed to listen to one of two different stories, which were played simultaneously. The first one was played into the participants' right ear, and the second was played into their left.

For the people who had slept eight hours the night before, this was pretty easy. They had no problem recalling details and staying focused. When looking at their brain activity, there was one enhanced signal that represented the story they were paying attention to. The sleep-deprived group didn't do nearly as well; they struggled to stay focused on one story because their brains couldn't concentrate. The neurological signal was much less enhanced, which means that deprived participants were dividing their attention between the two stories.

Not only is this kind of multitasking confusing, but it also affects other major brain functions. Memory encoding, retrieval, and comprehension all decrease when you can't concentrate. So please do yourself a favor and get a full eight hours. Otherwise, you're gonna spend the whole day wondering what you're missing.

2. Higher Cognition

Even if you can pay attention, chances are your brain just won't work like it normally does. Sleeping only three hours a night has a huge impact on most elements of higher cognition. That means everything from perception to memory, but some functions suffer more than others.

A 2010 study discovered a group of higher cognitive functions that go down the drain when your brain can't recharge and detoxify. Using neuroimaging, researchers saw that the prefrontal cortex experiences the largest decline in performance when sleep-deprived. The prefrontal cortex is the area at the very front of your brain; it's right behind your forehead. It's responsible for a wide variety of functions, which are usually called executive functions.

There's some of the most sophisticated things that your brain can do. Most people claim executive functions are what separate humans from every other animal on the planet. They're advanced, reflexive, and cognitively complex. Creative problem-solving is one of the best examples. It's our ability to think outside the box to discover unique solutions for intricate problems. But when you don't get enough sleep, your prefrontal cortex can't function like it normally does, so creativity and innovation naturally fall apart.

Oh, and it doesn't stop there. Higher cognition is often called emotion-dependent. In other words, certain emotional states allow you to think and behave differently. For example, when you're feeling happy, it's much easier to make reasonable decisions than when you're feeling sad. Since getting three hours of sleep decreases your mood, it impairs higher cognition even more.

Now, of course, most people think there's an easy fix: just drink a cup of coffee. Caffeine is an immensely popular stimulant that people use to wake up their body and brain. After 15 minutes, which is about how long it takes for caffeine to enter your bloodstream, you start to feel lively and attentive. It even improves your mood and motivation. So you'd think that this burst of energy would restore higher cognition, right?

Well, if you were lacking in creativity before, shouldn't a bit of caffeine get you back on track? Unfortunately, there's no easy replacement for a good night's sleep when it comes to higher cognition. A cup of coffee isn't nearly as effective. This finding stems from the same 2010 study. They analyzed what areas of a sleep-deprived brain were most affected by caffeine. Individuals who didn't get enough sleep but drank a cup of coffee experienced increased attention and alertness, but their creativity never got any better.

So don't let your lack of sleep slow your brain down. If you start sleeping eight hours each night, you'll feel more creative and perceptive than ever.

3. Dietary Decay

Everyone knows that foods like candy, chips, and french fries are bad for you. They contain excess amounts of sugar, salt, and starch. If you're not careful, eating a few unhealthy snacks each day can really add up. Salt, for example, increases your risk of high blood pressure, while sugar, after giving you a small boost, leaves you feeling cloudy and tired.

There are many reasons why you should avoid these unhealthy foods as often as possible, but sleep deprivation makes eating right much harder. You see, when your body doesn't get enough sleep, it can really control your appetite. On the mental side, your usual level of self-discipline is way down, meaning you have a harder time maintaining your healthy eating habits. To pile things on, sleep deprivation injects a significant amount of mental stress into your life. When you're feeling foggy and frustrated, you're more likely to choose tasty yet fattening snacks. They provide a much-needed neurological reward, even though they ultimately hurt you in the long run.

Physically, sleep deprivation messes with hormone production. It starts by stimulating a hunger hormone called ghrelin. Normally, ghrelin tells you when you've got an empty stomach, but if you have too much ghrelin in your system, your hunger never goes away. Those excess hormones continuously trick your body into overeating. Ghrelin will keep sending more and more hunger signals long after you've eaten your fill.

And to make matters worse, sleep deprivation subsequently inhibits a hormone made by your small intestine called leptin. Leptin regulates your body's energy levels by telling your brain when to stop nourishing itself. So without leptin, you'll accidentally eat way more food than you're supposed to. More food means slower digestion, more fat storage, and an uncomfortable episode of heartburn.

Now, you combine all that with the negative impact of the actual foods that you're eating. Starch, for example, is a natural appetite inhibitor. Even if you're sleeping eight hours a night, too much starch can ruin your diet. But when your hormones are already dysfunctional, overeating is almost inevitable. As you can see, a simple lack of sleep can quickly snowball into a much bigger problem.

Effects of Poor Sleep on Health

But how does this combination of sleeplessness and a poor diet affect the rest of your body? Well, let's run through some important statistics really quick. If you sleep less than three hours a night, you're about 48 percent more likely to develop heart disease. That seems like a lot, right? Well, it makes sense when you consider that you're increasing the risk of obesity by about 50%. Sleep-deprived people are more likely to eat unhealthy foods and more of them. Not to mention, you're less likely to exercise when you're feeling tired.

You're also three times more likely to get sick due to lower immune function. You're prone to common mental illnesses like major depression and chronic anxiety. By catching and correcting bad sleeping habits, you can dramatically improve your daily and long-term health.

4. Increased Mortality

Unlike the other items on this list, drowsy driving doesn't have a long-term impact on your cognition or health, but that doesn't mean it's any less important. In fact, over 70,000 car accidents happen every year from drowsy driving. Around fifty percent of those accidents result in major injury, and another ten percent are fatal.

Compared to driving under the influence, drowsy driving doesn't seem that bad. So you're a little sleepy, what's the big deal? What's the worst that could happen? Imagine one night you're cruising down the freeway at seventy miles per hour. It's just you and a few other cars, so you're not paying all that much attention. You've got the heat on, so the car is warm and cozy. You're listening to some soft music. Since you've got cruise control, your foot isn't even on the gas. Slowly but surely, your eyes start to close.

Before you know it, you're not even looking at the road anymore, until suddenly your body shocks itself awake. You stare out the windshield, wondering how long you'd closed your eyes. Even if it was just a few seconds, that's more than enough time to run head-on into a divider or another car. At 70 miles per hour, it's very likely that a collision would result in significant injury or death. And that's all because you didn't get enough sleep the night before.

The biggest problem with drowsy driving is how incredibly common it is. For example, most people are exhausted after a busy day at work, but they still have to commute home in the afternoon. It can happen to anyone, but if you're not getting eight hours of sleep, then you're putting yourself and everyone around you at risk.

So no matter how hard you try to focus, your brain won't be as attentive and aware later in the day. It'll be harder and harder for you to stay awake. So getting enough sleep isn't only good for your body and your brain, it might just save your life.

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