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Lack of sleep causes cognition and memory problems

Updated on April 17, 2016

Do you remember sitting in homeroom the day before the SATs? At my high school, we were drilled for months in preparation for the SATs and ACTs—how well juniors did on these tests had something to do with how much funding the school got from the country. On the Thursday before I took the SAT, my homeroom teacher, who was also my AP Literature teacher, gave a list of things that we needed to know about the test: what to bring, what not to bring, when to show up, where to go, etc.

At the top of the list, in all caps and in a font larger than the rest of text, was written, “GO TO BED EARLY AND GET PLENTY OF SLEEP.” She was a very severe woman, so when she looked at us over her glasses and told us she was serious about that directive, we took her seriously.

Lack of focus and mistakes

Why did it matter when we went to bed or how much sleep we got? Most of us had been studying for months for the Scholastic Aptitude Test and were more than prepared for what was coming. It mattered because sleep and cognition are deeply linked.

You’ve probably felt the effects of too little sleep, at least acutely. You have trouble focusing. For many people, this sets in somewhere around 3:00 pm at work. You lose the sharpness that you had when you first arrived at work and tasks that you know how to do suddenly become tedious or confusing. You might not even realize it is happening until you look back over your work and realize that you have made a series of mistakes that you would never had made, if you were not tired.

Why are sleep and cognition so deeply connected? And how do you know if you are getting enough sleep? What are the most common sleep deprivation effects?

How does lack of sleep affect your cognition?

Have you ever heard someone say that they feel “foggy?” lack of sleep or chronic sleepiness can actually slow down your brain’s ability to process information. For example, if you were to solve a math problem, it would take you much longer to solve that problem if you were sleepy than if you were perfectly rested and alert.

It dulls the centers of your brain having to do with logical reasoning and, perhaps more importantly, complex thought. Even simple decisions become difficult to make, as the parts of your brain that govern those abilities cannot function properly when you have not gotten enough sleep.

lack of sleep also affects your ability to both make new memories and to recall existing memories. Sleep psychologists believe that sleep gives the brain time to process all of the information it has collected during the day—sights, smells, and sounds. It is during sleep that our memories are cemented, it embeds what we’ve experienced and learned into short-term memory.

Without enough sleep, the short-term memory begins to fail. Not only will you find yourself having a more difficult time recalling things you once knew, you’ll be less able to make new memories. This is partially because you cannot focus properly while sleepy, but also because your brain does not have the power to embed information into your memory.

This is why people who do not get enough sleep have a difficult time learning even simple subjects. The brain loses its ability to focus and memory is dulled. Without focus and short-term memory, cognition cannot happen.

What is enough sleep? How much sleep do I need?

You’ve heard it a hundred times: get plenty of sleep. When you’re sick, you hear it from your doctor (and your mother). When you have a test, performance, or presentation coming up, you hear it again. But what constitutes “enough” sleep. There actually is a thing as oversleeping, that isn’t just bad for your schedule, it’s bad for your brain, too.

The right amount of sleep varies from demographic to demographic, with teenagers and children needing the most sleep and adults needing the least—but that’s not to say that they don’t need any sleep at all. How much sleep you need, as an individual may vary slightly from the numbers assigned to your age range.

Many people are productive and happy with only eight hours of sleep, while others need a full nine hours or they are hopeless for most of the day. Those with special health conditions, like obesity or a heart condition, may need more sleep than someone who is in peak physical healthy. Keep in mind that the following numbers are a general rule only and that finding your perfect number of hours will take some trial and error.

Newborns need the most sleep, at twelve to eight hours per day. Infants are next on the list, with fourteen to fifteen hours of sleep. Toddlers can do alright on twelve hours of sleep, but your one to three year old may need upwards of fourteen. Preschoolers (ages three to five) should get eleven to thirteen hours, while those in primary school need only ten to eleven hours. Teenagers need at least eight hours of sleep, but could get upwards of ten.

Adults are at the bottom of the list, needing seven to nine hours on average. Again, the exact number of hours you need will vary depending on your lifestyle, how much caffeine you drink, and your health.

Do you lose sleep more than once a week? Having less than 7h-8h depending on your need.

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What happens if you get two hours less sleep than you need each night?

If you go for more than two days in a row without getting the required amount of sleep, you are likely to start to feel a numb of negative side effects, including a number of side effects that relate directly to your cognition. Even if you only get two to three fewer hours of sleep you need ten days in a row, your cognition slows to a snail crawl. Why? Because your brain has not had the “down time” it needs to properly process all of the information coming in through your throughout the day. It is being overloaded with data and is not being given a chance to fully embed it into your short-term memory.

A recent study tested the resting heart rates of individuals who got eight hours of sleep per night, versus the heart rate of those who only slept four hours per night. Those who only got four hours of sleep, had abnormally high heart rates and blood pressure—two indications that a person is at risk for heart disease. While some of the most severe side effects do have to do with the brain, there are a number of physical side effects that can be just as damaging.

Studies have also shown that those deprived of sleep, even just a few hours a night, can’t remember things they learned just twenty-four hours before, showing a tangible decline in their cognition, as well as their ability to make decisions and or think logically. When you lose sleep, you are effectively dulling your brain, making it impossible to function properly.


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    • Sam Shepards profile image

      Sam Shepards 21 months ago from Europe


      Thanks for the response. We'll I don't have difficulty sleeping in general, but I do it myself. Staying up late, maybe watching another episode. Getting into bad sleep habits. I do programming for a living so I need my focus and sometimes I do suffer from my own mistakes in this regard. :)

    • fpherj48 profile image

      Paula 21 months ago from Beautiful Upstate New York

      Sam....I'm pretty diligent when it comes to getting "enough" sleep. I can honestly say that I've learned through the years that I simply have to do this. For me there is no getting around the fact that a lack of enough good sleep and I feel terrible~ useless sometimes~ Fortunately I've never had to struggle with any sort of serious sleep difficulty.

      This is a great informative read. Thanks for sharing.