Why do we spend (or should spend) 1/3 of our day sleeping? What do we get out of it? Have we found here the great mistake of evolution? The case study that would leave Charles Darwin spinning in his grave?

We have all heard someone say that sleeping is a waste of time and that there is no logical reason for why we should lie down for 8 hours a day, with our eyes closed and without moving a muscle. In line with this same argument, I would also add that while we are sleeping we are not searching for food, we are not mating or looking for a mate, thus ensuring the continuation of the species and, moreover, we are completely vulnerable to attacks by any predator (which in the case of humans could be, perhaps, a mosquito). Not quite convinced of the importance of sleep yet, are you?

The truth is that nature wastes no time. No physiological process has yet been found to be redundant, that is, whose existence is not necessary. Yes, and even the poor appendix, so devalued by everyone, has its function (it plays a very important role in stimulating our intestinal microbiome).

Certainly, a process whose expression occurs in all species without exception, that reduces the state of wakefulness to dangerously low levels must have an indispensable function. And it does!

Sleep plays its role in practically all our systems and organs. It is so essential that, even in the middle of a migration, birds cannot escape it and sleep in mid-flight. In the marine kingdom, even though these animals are condemned to swim until eternity, they do not do it without sleep and sleep with one hemisphere at a time. As you can see, there is unanimity regarding the importance of sleep for the species that inhabit the Earth. But there is one species that was not present in this counsel. Can you guess which one?

The human being, of course! Humans and their powerful intellect are, once again, the pioneers in an extraordinary achievement! We are the only ones who deliberately and intentionally deprive ourselves of sleep! Our reputation precedes us! We all know that one of the main characteristics of our species, and the one that makes us more proud is the exquisite disregard for our own natural needs and rhythms. And of course! Sleep could be no exception!

Okay, Rui, we’ve had enough of this… So, tell us what are these benefits? — you are thinking while reading this text. Calm down! One thing at a time…

Sleeping more means living longer. Science is unanimous on this fact. Sleep deprivation has a dramatic impact on our cardiovascular health, immune system, brain, weight, and many others. And all of these factors have a direct impact on our health and longevity.

But before I stick you to the wall with studies and scientific data about how dramatically shorter your life will be if you don’t get the recommended number of hours of sleep, let’s explore a bit what this sleep thing is.

Our sleep can be divided into REM and NREM. During REM (rapid eye movement) sleep, as the name implies, rapid movements of our eyes occur and it is the type of sleep in which dreams occur. This means that we dream every night! We hear a lot of people say “I dreamed so much this night!”. What people are really saying here is “I remember most of the dreams I had tonight!”. Every night, immediately after we have dreamed, our brain erases the memory of that very dream. However, if we awake during the process, it is normal for that memory to persist, and therefore we remember the content of our dreams. If this awakening does not occur, our dreams will be eliminated from our memory and we will not be aware that we spent a significant portion of our night dreaming. During this phase, something we call atonia also occurs. This process paralyzes our body, preventing us from acting-out our dreams. This state of atony in certain specific cases is responsible for what we know as sleep paralysis. What happens is that even though our brain is already waking up, it still can’t temporarily release the body from the prison caused by it, resulting in an active brain but without the ability to move the body. Everyone who has experienced a situation like the one I described understands how panicky it is to be trapped in your own body, unable to move or even speak. A scene worthy of a horror movie, isn’t it? Our brain has a great sense of humor. In these transition periods between waking and sleeping (or vice versa) hallucinations can also occur. These are called hypnagogic and hypnopompic hallucinations. During these episodes people may have visual, tactile, or auditory perceptual experiences. The good news is that they are a transient phenomena, lasting only a few (long) seconds. Finally, during REM phases there is intense and unsynchronized brain activity, very similar to that experienced during wakefulness.

During NREM (non-rapid eye movement) sleep, unlike the REM phase, there are no eye movements, and it is characterized by slow brain activity. This phase is further divided into 4 phases (N1, N2, N3 and N4). Phases N1 and N2 are a transition between wakefulness and sleep, and phases N3 and N4 are called slow wave sleep and correspond to deep sleep.

During a full night’s sleep (between 7 to 8 hours — yes, you read that right), these two types of sleep occur in alternation and varying duration over 4 to 5 cycles. Each sleep cycle lasts about 60 to 90 minutes. At the end of each cycle an increase in wakefulness levels occurs. Also, the “recipe” for the various sleep cycles is variable with respect to the amounts of REM and NREM sleep. For example, in the early evening NREM sleep predominates, and at the end of the night our cycles are filled almost entirely by REM sleep.

from “Why do we sleep” — Mathew Walker, PhD

What happens when we decide to delay our sleep onset or wake up earlier than we are supposed to, is that this cycle is interrupted. Depending on how this interruption occurs, different consequences can arise. When we lose NREM (early night) sleep we compromise, for example, our ability to consolidate information in our memory from the day before, we impare our ability to learn on the next day and, for example, compromise the recovery and restoration of our cardiovascular system after intense activity during wakefulness. When we wake up earlier than we should, we lose a huge amount of REM sleep, which will have a dramatic impact on our creativity, problem solving, decreased negative emotional activation, and even learning new languages!

A while back, a myth was spread that humans would only use a small percentage of their brain’s “full capacity”. As a young psychology student beginning the study of the human brain and behavior, this idea seemed instantly ridiculous to me.

However, as I began to study sleep, I realized that this myth may then have some truth to it. And no, I am not talking about the possibility of unlocking hidden telepathic or telekinetic powers only discovered by monks in ancient China.

The recipe for unlocking this full capacity of our brain is actually quite simple (and perhaps more boring): 7 to 8 hours of sleep per night.

About 1 in 3 people live in a state of chronic sleep deprivation, which means they live with this “blocked brain syndrome”. When we don’t get enough sleep we are doomed to live in a suboptimal state of performance and health.

So the question is not whether we can unlock hidden skills in our brain. The question is whether we are not blocking them with insufficient sleep.

This is the first post from a series of texts that i’ll write, where i’ll be talking about sleep and several related subjects, such as, the function of sleep in our many systems and organs, the consequences of sleep deprivation, circadian rhythms, chronotypes, sleep through the life cycle, and many others.

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