Why we SleepOn June 12, 2019 by neurotravels
S L E E P.
The book I recently picked up is an absolutely fantastic read, in a lot of different ways. The author, Matthew Walker is an inspiring scientist and science communicator. In “Why we sleep” he tells the story of sleep in such a fascinating, detailed and accurate but still highly accessible and easily understandable way, it is simply fun to read and hard to put down! I can nearly guarantee, that it will change your view on your sleeping routine!
I’m currently working in a lab that deals with sleep and cognition. Most of our studies involve sleep measurements (- not in humans, but mice), the manipulation of sleep and the consequences thereof. My own research had so far little to do with sleep experiments and – to be honest – in my days at Uni I was never particularly interested in studying sleep. But, being surrounded by sleep research, and getting insights into how IMMENSELY important and undervalued it is, in both health and disease, my passion for it just keeps growing.
So… Why do we sleep?
I’m a big fan of evolutionary studies and anthropology. Sleep is an evolutionary aaancient and highly conserved thing. So, what does that tell us? In general, if something is “evolutionarily old”, that means it surfaced very early in the timeline of life on Earth. If something is highly conserved, it means that you’ll find it across a lot, if not all, animals or even living organisms on the planet. Conserved basically intents that evolution didn’t get rid of it up until now. If something has become useless or disadvantageous for survival of the species, it (or, if too late – the whole species) would’ve gone extinct. Some things that are evolutionarily highly conserved did even evolve more than once, parallel, in a slightly different way and independent of each other, one prominent example being eye-sight. This fascinates me incredibly, still!
Pictures modified from Cris Saur, Matt Flores, Zdeněk Macháček on Unsplash
Everything sleeps. Worms sleep. Dolphins sleep. Cats obviously(!) sleep. Koalas sleep (a lot!). Humans sleep. Like most animals, humans sleep about one third of their life. One third! About 30 years of sleep, in a 90-year-old. A third of our life in a state where we are unconscious, lying flat on the ground (bed), able to do nothing but rest. What a waste of time!? Well – probably not. Given how widely distributed sleep is and that evolution just could not get rid of it over millions of years, even though it is in the direct way of every living thing’s drive to survive, eat and reproduce, should outline its importance.
You might have heard of the famous sleep scientist Allan Rechtschaffen saying:
“If sleep doesn’t serve some vital function, it is the biggest mistake evolution ever made”
How we mess up sleep…
Apparently, humans have become unaware of the natural, critical time we rest in bed. We cut it short, we manipulate and ignore our sleep/wake cycle for and through work, sport, drugs, parties, relationships, staring at screens. Our need for sleep is directed by an inner “body clock”, the circadian rhythm (that even plants have!), which is influenced mainly by light (think: screens), and also by our internal sleep pressure, which builds up while we are not sleeping and decreases while we are – and the both, interestingly, work independently from each other.
So, what does sleep do and what is it so crucial for? Research in this domain is still ongoing, but we’ve learned a lot in the last decades. We do now know how critical sleep is for attention (important for everyone driving a car, as Walker outlines in his book!), memory building and recalling, concentration, performance in sport, and for mental health. Lack of sleep makes you moody and irrational, builds short-term extremes of happiness, sadness and aggressiveness. It increases your craving for unhealthy food, and in general decreases your capability of inhibiting things that you normally wouldn’t do.
Sleep in Health and Disease
Sleep is messed up in basically every non-healthy condition that you can think of.
In health, while you’re lying there in bed, partially completely immobile and always unconscious, you rest. Your body rests, and your brain – does beautifully weird things. Maybe counter- intuitively, your brain is active. If undisturbed, it’s active in a harmonic, predictive way, goes through different phases and “depths” of sleep while your eyes are shut throughout the night. It goes through phases of deep sleep, where your brain waves dance highly synchronous like synchronised dancers in the water, it goes through dream sleep, where (you might remember), you come up with the weirdest stories.
We know that ALL of these forms of sleep are critical. Some are for strengthening memories, building connections, and potentially testing them out. And for others, evidence is pointing towards its importance for getting rid of unwanted stuff. Someone has to deal with the too many connections, unused connections, or simply, waste, trash, that has been accumulating over the day. This is an elegant clearance system, a system getting rid of products that we otherwise might accumulate too many of, and that could lead to big problems. We see unusual sleep in patients of trauma, stroke, Alzheimer’s Disease and other forms of dementia, depression, anxiety, post-traumatic stress disorder and the list can be continued.
Sleep – an underestimated, powerful, natural, free, invaluable, beautiful, relaxing, healing state we can use to our advantage, every single day: do 8 hours a day at regular times of day. It’s a short- and long-term investment into your physical and mental health.
Have a good night!