Why is sleep important? We ask neuroscientists, doctors, and NASA

Sleep. We all do it, and some of us do it better and for longer than others. But why do we sleep and why is sleep important? These may seem like obvious or basic questions, but the answers are neither obvious nor basic, as a lot of human sleep remains uncharted territory. Science now knows more about it compared to even ten years ago, but most sleep experts agree there are still many riches to discover.

Type the word ‘sleep’ into Google, as many people are during Sleep Week, and you’ll be met by a sea of articles discussing why sleep is important – and why it can sometimes be so difficult to fall asleep. Regular questions include, ‘How many hours of sleep do you need?’ and ‘How can I sleep instantly?’ As a species, we seem obsessed with slumber numbers: how much, how fast, and also what does our age have to do with it? And it isn’t just Google being asked why sleep is important – doctors are regularly quizzed, usually by folk who are at their wits’ end over poor sleep.

For some, good sleep is an elusive beast, and cruelly it seems like the more a person struggles to sleep, and the more effort they put into trying, the more they struggle. And on it goes. But understanding the importance of sleep and how to let it happen (because we can’t make it happen), the sooner you’ll return to what feels like healthy, happy snoozing for you. It’s also worth remembering – as neuroscientists and sleep doctors are now reminding us – one size does not fit all when it comes to getting some decent shut-eye.

WHY DO HUMANS NEED SLEEP?
The average person spends nearly a third of their life asleep, and if we keep skipping on quality sleep, the outcome won’t be good. Consistent poor sleep damages the body, and total, prolonged sleep deprivation can be fatal. Dr Lindsay Browning, neuroscientist, chartered psychologist and author of Navigating Sleeplessness points to a very rare genetic brain disorder associated with lack of sleep which can be fatal: “Without sleep we [eventually] die. There’s a condition called Fatal Familial Insomnia, where people stop being able to sleep and the only outcome of that is death.”

While such examples are extreme, they show that sleep is important. However, from an evolutionary perspective sleep makes no sense. Dr Browning explains it best: “When we sleep, we are completely vulnerable. We are at risk to predators and the environment around us. From that perspective sleep is a very risky thing to do, so it must have huge benefits that outweigh those huge risks of death.” We have to admit, thinking about sleep from this perspective is new to us, but it’s certainly thought-provoking.

Sleep impacts, and is impacted by, nearly all other aspects of human physiology."

– Dr. Erin Flynn-Evans, NASA
NASA has also spent a long time thinking about sleep, why we need it, and how to get it. For more than 50 years, NASA’s Human Research Program (HRP) has been studying what happens to the human body in space, and one ongoing element of that research is sleep. Chiefly, how to ensure astronauts get quality sleep in space, and what the repercussions are if they don’t.

Dr. Erin E. Flynn-Evans, previously an instructor in Medicine in the Division of Sleep Medicine at Brigham and Women’s Hospital and Harvard Medical School, now leads the NASA Ames Research Center Fatigue Countermeasures Laboratory. Who better for us to ask the big question, why do humans need sleep? “This is a very challenging question!” says Dr Flynn-Evans. “Humans need sleep for a variety of reasons. Sleep impacts, and is impacted by, nearly all other aspects of human physiology.

Why is sleep important: A happy woman wearing a yellow jumper and blue jeans jumps in the air

(Image credit: Getty)
“Sleep enables physical recuperation of the body, encodes memories, enhances learning, suppresses metabolism, restores cognitive function, and may even help the brain clear waste products.

“At NASA, we care about all these benefits, but one of the biggest reasons we study sleep is to ensure that astronauts are able to perform at an optimal level during missions including to the moon and Mars.” While most of us aren’t ever likely to set foot on the moon or Mars anytime soon, if NASA recognizes the vital importance of sleep, then the rest of us should too.

WHY IS SLEEP IMPORTANT TO OUR HEALTH?
For something we’re supposed to do naturally, sleep sounds complex. But what can science tell us about what happens to our brain and body while we’re asleep? Dr Katherine Green, MD, is the Medical Director of the UCHealth Sleep Medicine Clinic, and she will also soon be talking about all-things-sleep in the new women’s health podcast evrē. She helps us shed some light on how sleep affects the brain: “Key processes involved in learning and memory happen only during sleep, and sleep is an integral part of memory consolidation and learning and retaining new things,” says Dr Green.

“There are vital roles in regulating mood and appetite that depend on your circadian rhythm and the cycle of wake and sleep. Recent studies have shown that during sleep, there are vital ‘housekeeping’-like processes that occur to clear toxins and by-products from the brain that build up during periods of wakefulness.”
This is something Dr Browning spoke to us about too: “We know that when you sleep, your brain physically spring-cleans itself of amyloid plaques, which are sticky protein substances that build up and cause Alzheimer’s. If you aren’t sleeping enough, your brain has to prioritize what it really needs to do in a shorter period of time because you are having less sleep.”

In an article titled The Sleep Deprived Brain, the Dana Foundation shared how, “A new study now shows that just one night of sleep deprivation results in the accumulation in the brain of a protein implicated in Alzheimer’s.” So much for your brain ’switching off’ during sleep, huh?

The UCSF Weill Institute for Neurosciences is home to researchers and physicians studying some of the most complex challenges in the human brain. Dr Louis Ptacek is a professor at the Department of Neurology there, and when we pressed him for an answer on why sleep is important to humans, he told us straight: “We really don’t know. It’s clearly important for ‘restoration’. Probably eliminating some ‘waste’ that has accumulated during the day. What we know for certain is that chronic sleep deprivation leads to increased risk of many diseases. So getting enough sleep is important.”

Dr Browning backs this up: “So much research consistently shows that getting enough good-quality sleep is associated with diminished risk of depression and anxiety. You also have a decreased risk of getting certain types of cancer, of getting dementia, of obesity, and strokes. Your immune system benefits if you sleep well, as does your memory and your ability to make decisions.”
While there are still question marks over its precise function, and exactly what happens to us during sleep, we are now understanding that healthy sleep is just as (arguably, if not more) important as getting regular exercise and eating a healthy, balanced diet.

But even then, it’s tempting to cut down on sleep in favor of doing something else a little more, well, exciting or productive. That could be getting up at 5am to hit the yoga studio, or going to bed late to nail a massive work assignment that’s giving us anxiety. Or heck, just staying up way past our bedtime to kick back and watch a movie. Yet if we don’t prioritize sleep, all of those things will be harder or less enjoyable.

As part of her work teaching Cognitive Behavioral Therapy for Insomnia (CBT-I) at Trouble Sleeping, Dr Browning has met with a lot of sleep-deprived people who sacrifice sleep to make gains in other areas of life.

If people don’t understand the benefits of getting good sleep, they naturally won’t prioritize it and will do other things."

– Dr Lindsay Browning
Some folks see sleep as an inconvenience that gets in the way of a busy, fulfilling life, while others don’t necessarily understand the importance of sleep because they can’t see the direct effects of getting good sleep in the way they do when lifting weights or writing a novel, for example. Muscles get bigger and words mount up on a page after a while, but how do we directly see and measure the benefits of sleep over a longer period of time?

“With sleep, some of it is direct – your immune system is compromised after just one night of poor sleep,” Dr Browning points out. “But if people don’t understand the benefits of getting good sleep, they naturally won’t prioritize it and will do other things. That does make sense, but that’s also why it’s vital to educate people that sleep is important and to prioritize it just as you would healthy eating and exercise.”

In other words, while we are inundated with information on the importance of getting regular exercise, or eating at least five portions of fruit and veg a day, when it comes to discussing the role of sleep, it doesn’t get nearly as much air-time. Dr Browning wants people to think about sleep in the same way they think about the benefits of regular exercise and a balanced diet: “I want people to think that if they prioritize sleep, they’re benefiting themselves just as they do when choosing to eat more fruits and vegetables and choosing to exercise.

“We need to do all of these things to be healthy, and not sacrifice one for the other. What pains me is when people get up two hours early to go to the gym before work, but they might not be going to bed two hours earlier. So those people are sacrificing sleep and doing damage to themselves.” Hats off to those who adjust the time they go to bed to accommodate getting up earlier.
Before we explore further, it’s important not to get hung up on the concept of ‘good sleep’ because healthy sleep for you will be different to healthy sleep for the next person. This is why you shouldn’t panic, because poor sleep is, for the majority of people, something that can be addressed by a doctor or sleep expert. It also pays to keep some perspective – a crumby night’s sleep here and there is not the end of the world.

This preoccupation with achieving correct sleep, also called Orthosomnia, is something Dr Browning has experience of dealing with, “My work is helping people who are struggling to sleep, and so often their struggles are fueled by, ‘Well, I read that if I don’t sleep for seven to nine hours I’m going to get cancer. And then of course that person doesn’t sleep well because they’re stressed out of their mind about their sleep.

“I deeply believe that sleep is important,” she continues, “but I really want to balance that with making sure that people don’t obsess about sleep because that can be damaging.”
We asked Dr Salvaterra, of Johns Hopkins Community Physicians Pulmonology and Sleep Medicine, what the impact would be on our physical and mental health if we didn’t get enough quality sleep on a consistent basis. She replied, “Various health conditions associated with poor sleep include mood disorders, cardiac arrhythmias, and memory impairment. Even dementia has been associated, along with stroke if there is lack of oxygen to the brain in people with sleep apnea.”

For Dr Salvaterra, the importance of sleep is perhaps best answered by looking at the effects of sleep deprivation or poor sleep: “When we are deprived of sleep the brain function is impacted as memory is affected, with inability to pay attention at tasks and loss of creativity.”
As Medical Director of the UCHealth Sleep Medicine Clinic, Dr Green has also encountered a lot of people with varying sleep issues, and is well-placed to talk about the effects of poor sleep. “Health benefits of sleep are very wide reaching – studies show that getting insufficient sleep increases your risk of high blood pressure, cardiovascular disease, metabolic disorders such as diabetes and obesity, and also increase the risk of anxiety and depression. We know that poor sleep impacts cognition, learning and memory, focus and attention, and also impacts driving and work safety.”

Sleep also has links to fertility, with irregular sleep cycles potentially causing issues when it comes to baby-making. “Circadian rhythm and the hormones that regulate sleep and wakefulness also trigger the release of the daily hormones that regulate both ovulation and the process of sperm maturation,” explains Dr Green. “So if your sleep cycle and sleep habits are not regular, there may be dysfunction in the timing or regularity of those hormones being released, and this can lead to menstrual irregularity or a prolonged period of trying to conceive unsuccessfully.”