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How Your (lack of) Sleep is Killing You

And what to do about it

Posted on February 08 2020

Suddenly, Arianna Huffington collapsed. She had been on the phone during one of her routine 18-hour work days. Awaking, bloody with a broken cheek bone, Arianna knew that she needed help.

Weeks of medical tests, and still there was no clear understanding of why she fell. Finally, her doctors came up with a simple explanation: chronic exhaustion. She was not sleeping enough.

She’s not alone though.

We All Need More Sleep

We desperately need sleep; our culture is massively sleep deprived. One study showed an estimated 40.6 million working adults do not get enough sleep. That’s almost a third of the working population, and that percentage increases when you consider vital jobs like those in health care.

Not Sleeping Is Really Unhealthy

Lack of sleep has serious consequences, with high rates of burnout among medical interns partly due to poor sleep, and links between sleep deprivation and surgeon burnout and surgical errors. Just as terrifying, airplane pilots show an increased risk of crashing when they don’t get enough sleep.

Lack of sleep leads to errors and accidents in general. Sleep deprivation can increase risky behaviors, like driving tired, and around 20% of car crashes are linked to drivers needing more sleep.

Sleep related accidents are estimated to cause around 50 Billion dollars worth of damage a year. This may be due to the fact that our motor function (ability to perform complex and coordinated movements) can be seriously impaired from lack of sleep, which can have a similar effect as alcohol.

But why would you drive, perform surgery, or fly a plane while sleep deprived? Well, there is research showing that decision making is negatively influenced by sleep deprivation. This can lead to increased risk-taking behavior in some cases.

If poor sleep can lead to job burnout, critical mistakes at work, car crashes, poor decisions, and risk taking, what is going on in our minds?

Summary of the Cognitive Theories of Sleep Deprivation

There are two general theories. One is that our functioning is not impaired most of the time when we are sleep deprived, but that short burst of near-sleep like activity (‘microsleeps’) in the brain leads to decreased performance. The idea here is that we sporadically come close to falling asleep, which leads to a loss of functioning.

The other theory is that the increased sleep related activity in the brain leads to general cognitive instability. This would be something like the notion that when we don’t get enough sleep, our waking brain activity more closely resembles sleep, in essence we are partially asleep. Both theories predict failures when it comes to performance, especially as the time on task increases. More on the neuroscience later!

We Think and Perform Much Worse When We Don’t Sleep Enough

So what other kinds of problems appear when we don’t sleep? A large body of research shows that our ability to think and work effectively goes out the window.

For a sleep deprived person, as the time required for a cognitive task increases, performance decreases. Essentially, you fatigue more easily.

There is a whole list of cognitive and performance deficits when it comes to sleep deprivation. To name a few:

  • If you have not slept enough, you’re likely to experience increased errors on tasks that require intense attention.
  • When you have the option to decide the pace of a task, you’re likely to finish the task at a slower pace. If there is time pressure, you will probably experience increased cognitive errors, and your performance will deteriorate as the time spent on the task increases.
  • With less sleep, your response time also slows. Both short-term recall and working memory abilities decline. Your capacity to learn new cognitive skills will be negatively affected, as will your creative problem solving.
  • You are likely to have trouble suppressing incorrect responses and will have an increased likelihood of sticking with incorrect answers for longer periods of time.
  • You’ll notice that more effort is required to stay effective on tasks, and you’ll find yourself neglecting activities that are not immediately essential. Situational awareness — or the perception and tracking of change of different elements in your environment — also decreases with poor sleep. This may be another reason why sleep deprivation is associated with accidents.

Overall, sleep deprivation “strongly impairs human functioning.

More In Depth on the Cognitive Theory of Sleep Deprivation

Some of these impairments in judgment, attention, and learning seem to be related to an area of the brain known as the prefrontal cortex (PFC). This area is one of the most recently evolved areas of the brain. It’s on the outermost layer of your brain, the farthest away from your brainstem, and is normally thought to be involved in executive functioning. Basically this part of the brain does the job of an executive or leader in any organization, except in this case the organization is possibly the most complicated in the universe, i.e. the human brain.

The PFC is involved in planning, impulse control, deciding between multiple possible options, and continuous monitoring and updating behavior, among other things. The PFC is basically required to do things like stay on task, update models of a task, suppress incorrect answers, and learn new cognitive skills. In essence, impaired functioning in the PFC would line up pretty well with the above list of known impairments in cognitive functioning that come from sleep deprivation.

There is evidence that sleep deprivation leads to decreased executive functioning, especially when it comes to unfamiliar tasks. Neuroimaging studies show decreased activity in the PFC after sleep deprivation.

Sleep, Stress, Mood, Aggression, and Relationships

While these decrements to performance are significant, the impairments in mood are much more pronounced. Interestingly, the negative effect of sleep deprivation on mood seem to be the most negative when the people in the study only got a partial nights sleep. This seems to indicate that only getting a few hours of sleep might be worse for your mood compared to going a while without sleep. Remember here the two models of sleep deprivation, which is sporadic moments of falling asleep, and just generally more sleep like activity in the brain.

The exact mechanism by which sleep negatively affects mood is not clear. So researchers started from the beginning, looking at the relationship between sleep and stress. There is evidence that stress and sleep deprivation are connected, but again, it was unclear how.

We know from a lot of research that stress and cognitive hyperarousal are related to insomnia. There is evidence that increased sympathetic nervous system (fight or flight) activity is exhibited by insomniacs. This is why some of the most effective methods for improving sleep quality are relaxation techniques like soothing music and guided imagery.

So stress causes sleeplessness, but does sleeplessness cause a worse reaction to stress? It’s hard to disentangle the two. So scientists designed an experiment. They deprived some people of sleep and then put them through a set of cognitive tasks. They found that people did indeed have more negative emotional reactions to stress when they were sleep deprived. Interestingly, the effect was significant when dealing with small amounts of stress. Partial sleep loss has been shown to increase stress hormones as well.

Lack of sleep has been shown to negatively affect mood in general. What’s worse, it seems that our own mood is not the only thing at stake. There is evidence that sleep deprivation can cause social conflict. One study found that people who were sleep deprived were more likely to blame others, and less interested in resolving conflicts. The researchers argued that we are more likely to act on feelings of aggression when sleep deprived. Other studies have found similar results, indicating that we may be more aggressive when we don’t get enough sleep. Again, these scientists argued that this increased risk of aggression may be due to impairments in the prefrontal cortex.

Lack of Sleep Makes Life a Pain

It has been known for a long time that chronic pain can cause insomnia and other sleep disorders. This makes sense, it’s hard to fall asleep while in pain. However, a recent body of research seems to indicate that poor sleep can actually cause pain, and increase the sensitivity to pain. The insomnia inducing effects of pain, and the pain inducing effects of insomnia can cause a vicious feedback loop, with one condition worsening the symptoms of the other, and vice versa.

Poor Sleep Causes Illness

Even partial sleep deprivation can cause changes in your immune systems response. One study found a significant decrease in the vital immune cells that normally kill tumors and infected cells (these are called natural killer cells). This sleep related impairment of immune system functioning is thought to be one of the reasons that cancer risk is increased in shift workers.

Sleep deprivation can also cause an increased inflammatory response. A study in rats indicate that prolonged sleep deprivation can lead to a breakdown of immune function so severe that it can cause death.

Another study found that, along with increases in inflammation, poor sleep also increased resting heart rate.

And another study found that poor sleep is associated with higher blood pressure. These results imply that poor sleep is a risk-factor for heart disease.

Adding to the risk of heart disease, there is evidence that not getting enough sleep can cause people to have increased appetite, and because they are tired, they have less energy and thus use less energy. The combination of being more hungry and less energetic is related to weight gain. What’s even worse, poor sleep changes the way glucose is regulated. This, combined with the changes in appetite and decreased activity level, can cause diabetes. For an examination of the relationship between appetite, energy level, and diabetes, check out this study.

Basically, poor sleep can cause some of the most common and dangerous illnesses.


If you don’t get enough sleep, you might find yourself getting into more accidents, taking more risks, performing worse, getting answers wrong, having trouble staying on task, getting more upset when you encounter small obstacles, feeling generally more stressed, having a harder time resolving social conflict, being more aggressive, feeling more pain, and getting sick more often. In short, it’s vital for your psychological and physical health and functioning to get enough sleep!

What to Do Next

It’s not all gloom and doom. In fact, there are plenty of ways you can improve your sleeping habits. To get started, read our 15 Tips for Great Sleep.

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