By Tomas Chamorro-Premuzic
Just like with most things, the value of sleep is most appreciated when we miss it. Sadly, this happens way too often, with around 30 to 40% of people experiencing sleep problems and a whopping 70 million Americans and 45 million Europeans suffering from chronic sleep deprivation.
Although there are always unavoidable circumstances that reduce our sleep, the numbers show that we often misunderstand the potential benefits sleep has on our lives, including our careers. More worryingly, there appears to be a general lack of awareness around the negative impact sleep deficit has on our physical and mental health. The fact that so many of us — along with our peers, coworkers, and friends — still take pride in losing sleep to do more work (as if it makes us superstar students or employees) is a clear example of this.
But when we choose work over sleep, what we are really doing is choosing quantity over quality. If you want to be the best version of yourself — at work, at school, and at home — it would be wise to take advantage of what a good night’s rest can offer: sharper focus, higher alertness, better endurance, and a more positive mood and mindset.
I’m sure you’ve heard this advice before. But the best way to understand the value of sleep is to digest some recent lessons from neuroscience — a field that has devoted a great deal of time to researching how sleep affects your brain, and what happens to your brain when you don’t get the sleep you need.
Your Brain Without (Enough) Sleep
Before we get into the specifics, let’s start with a quick overview of what your brain is actually doing while you snooze: Multiple studies show that your brain remains active and “online” while the rest of your body goes on standby. Your brain is a bit like your smartphone: You may not be looking at it during the night, but that doesn’t mean that it’s idle.
During sleep, your brain’s main function is to eliminate what scientists often call mental wastage — toxins that build up between your neurons throughout the day and that can impair your normal cognitive functioning in both the short and long term. Your brain does this in order to make room for more important and fresh learning experiences. Think of it like “auto-delete” on your laptop, permanently eliminating the stuff in your recycle bin to free up space and ensure faster processing speed.
This waste elimination is key to supporting your core learning and memory functions, as well as regulating your mood, emotions, and sexual appetite. In other words, sleeping is the human equivalent of refueling a gas tank. The idea that sleeping less to work more will somehow make you more productive is as logical as the notion that not stopping for gas will help you arrive at your destination faster. (So, not very logical.)
Here’s what can happen to your mind, your body, and your work when you miss out on too much sleep:
You forget how to do simple things. A single night of sleep deprivation is enough to disrupt the normal functioning of your hippocampus, the area of the brain that is central to memory and learning. The hippocampus plays a key role in helping you retain information in both the short and long term. It also determines how well you are able to navigate directions and move through space (which is why a famous study of the brains of London taxi drivers found that their hippocampus is larger than normal).
When you don’t get enough sleep, you might find that you are more prone to forgetting things, have difficulties concentrating, retaining numbers, or encoding facts. All these problems will have a serious impact on your job performance, unless you are on autopilot, doing repetitive or routine-like work. But even when you’re doing relatively easy tasks, you may notice a drop in your performance. This is why sleep deprivation may feel a lot like a hangover: It makes focusing painful, and you may need to focus much more on tasks that came naturally to you before.
Your long-term memory suffers. As noted above, sleep gives your brain time to get rid of metabolic waste, including proteins that can build up and form plaque between your brain cells. Over the short term, poor sleep has been associated with a lower IQ, and over the long term it has been associated with Alzheimer’s disease.
A review of 86 scientific studies found that people who tend to sleep longer are more agile, efficient learners, and they have a greater ability to keep their minds engaged, explaining why people who get more sleep are more likely to have a slower mental decline while aging. Better sleep hygiene contributes to better academic and job performance, as well as higher intellectual development. The more complex your job, the more you will have to learn, reason, and solve new problems — meaning that you will need more and better sleep.
You’re more prone to aggression and anxiety. Sleep triggers a chemical reaction in your brain that is essential for mood and emotional regulation. The main brain hormone involved in this reaction is called melatonin. Your body tends to produce more melatonin during the evenings to make you sleepy, and less during the mornings to wake you up. Melatonin has also been linked to mood alterations. This often happens when your body releases the hormone, signalling that it is time to sleep, but you ignore it and stay awake.
When a lack of sleep makes you feel grumpy, cranky, or irritable, as those around you are likely to notice, it’s because melatonin is affecting the amygdala area of your brain. You can think of the amygdala as an emotional radar that determines whether you are having a positive experience (“I feel safe”) or a negative one (“I feel angry or scared”). Your anxiety, aggression, and impulsive decision-making are all fueled by activity in your amygdala. Any changes that impact this area of your brain overnight will carry over to the next morning and affect your behaviour, including your capacity to be patient with others and empathise.
Negative emotions, like fear and anxiety, can also show up during your sleep in the form of frightening or disturbing dreams. And because you are more likely to be irritable and annoyed when you lack sleep, you may end up trapped in a vicious cycle whereby bad sleep destabilises your mood, which then disrupts your sleep in form of nightmares. All this to say, if you want to be a kind and caring coworker, partner, or friend, you should really get more sleep.
You put your relationships at risk. Sleep deficit may harm your romantic or personal relationships. Most adults sleep in the same bedroom as the person they live or co-habit with. When the above factors are at play, they will not just impact your own life and career, but also your partner’s. Unsurprisingly, there is a reciprocal effect between sleep and relationship quality: Being in a happy relationship will make you sleep better, and sleeping better will make your relationship better, too.
Even with all the research at our fingertips, I’m sure you will continue to hear your friends and colleagues boasting about how little they sleep, as if that makes them more productive or successful. When this happens, remember that science says the opposite: The more time and uninterrupted freedom you give to your brain, the sharper, happier, and healthier you’ll be when you are awake.
Tomas Chamorro-Premuzic is the Chief Innovation Officer at ManpowerGroup, a professor of business psychology at University College London and at Columbia University.
This article first appeared on Harvard Business Review.