Sleeping less than six hours a day increases the risk of having certain forms of cancer, Alzheimer’s disease, inconsistency of blood sugar, blockage of coronary arteries, psychiatric diseases such as depression, anxiety, suicidality, obesity and some other things. Sleep keeps our body’s metabolic state in balance by fine-tuning the insulin and circulating glucose. A good night’s sleep makes sure our gut microbiome is nutritionally plentiful, as well as our brain is refreshing itself. How is this biologically dumb-looking process important for our survival? I mean, we cannot gather/eat food, we cannot reproduce, we cannot socialize, we cannot protect ourselves and beloved ones while sleeping, because in sleep our all muscles are paralysed.

Our ancestors were used to sleep on trees, and at least 30% longer than us. Unlike them, we, the Homo Sapiens, did jump from tree to the ground and started to socialize more, check our phones before trying to fall asleep, wake up early to work till evening and then spend the money on unhealthy foods, playing computer games, watching Netflix with our friends, and so on. No surprise we are sleeping less than our primates. Interestingly, we also spend around 25% of our sleep time in REM (Rapid Eye Movement) phase, namely dreaming, compared to the average of 9% other primates dedicate their sleep time to.

There are two important factors that signal us the need to recharge. First is the circardian rhythm – our twenty-four-hour biological clock that is controlled by the suprachiasmatic nucleus, which sits above the crossing point of optic nerves. This biological clock creates a sleep-wake cycle that makes us feel tired or alert, respectively, using a circulating messenger hormone called melatonin. Second factor that pushes us to paralyze our muscles and refresh is the chemical compound called Adenosine. Adenosine is a sleep pressure that accumulates in concentration through every moment we are awake. The combination of highly concentrated adenosine and lower circardian rythym level triggers the desire for closing our eyes, drifting into the slow and relaxing void of the sleep.

Now we know why we need to sleep. Given the evolution, we have been following our circardian rythym and there is a sleep pressure that weighs heave when awake. However, the substrate of the sleep is not known. Adenosine is not a cause of sleep, it is a response of something else that we have not yet identified. Importantly, sleeping helps our brain to build new neural communications, which in return restores the brain’s capacity for making new memories, learning and contextualizing new information, connecting the freshly perceived data with the existing patterns. Actually sleeping helps us store and improve upon the knowledge to understand how sleeping works and why it is important. One day we’ll get there.

It brings us to the second point: ignorance of our modern community members on sleeping and many other things. We are very much hoping to pursue a meaningful and productive life, but without even understanding the basics of stuff. I personally did not have a broad understanding of sleeping before I read “Why We Sleep” by Matthew Walker. Also reading on the second law of thermodynamics, I can imagine that the sleep is the entropy or the waste we produce while having cognitive processing during the day. Building these patterns could not have happened, if I had not started to learn continuously. Building the habit of learning automates the process and makes it less effort requiring, which in return increases the efficiency, thus decreases the waste that sleep has to get rid of. Moreover, learning as a habit helps our mind to connect the ideas better during REM sleeps.

I can highly recommend “Why We Sleep” by Matthew Walker, if you’d like to also understand the importance of sleep.

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