Here’s a question we’ve all asked at least once in our lives: why do we sleep?
Sure, through experience, we all know the benefits of sleep. We’ve all felt what a good night’s sleep can do for our bodies. But a question we rarely ask of ourselves is: why do we even need to sleep? Why not some other process for recuperation? Seriously, why do we sleep?
What does history say?
Early concepts and theories concerning the reason for sleep are based upon our past as predators and prey. For example, a very early idea was that animals would be most vulnerable at night time so put themselves to sleep as a security measure.
This ‘inactivity theory’ basically argued that they would be safer because they remained hidden and undetectable whilst they slept. Although, this is often argued by pointing out that there’s nothing easier to kill than an unaware, sleeping target. Not very safe.
Another large theory (and, one that we already know quite well through the process of hibernation) is that sleeping is a form of energy conservation. It’s a bit of a dated theory nowadays, given that we rarely have to conserve energy or reserves. Instead we can just jump in the car and head to the shops.
But, in less accessible times, energy conservation could mark the difference between life and death. We burn up very few calories when we’re asleep, because our bodies aren’t doing much to really use up energy reserves.
That being said, these are rudimentary ideas, and seem difficult to apply to modern life.
So let’s dig into this further.
What happens when we don’t sleep?
It is both difficult and daunting to look down the barrel of such a philosophically loaded question as ‘why do we sleep?’- a recent BBC study of that same question started somewhere a little easier to digest: what happens when we don’t sleep?
The first thing to take a hit when we deny ourselves the luxury of a good night’s sleep is the brain. This is why sleep deprivation is a well-known form of military torture. Many special forces actually push their recruits through sleep deprivation training in order to test their mettle. It works since a tired mind is more likely to slip up and reveal secrets or information.
From the BBC: ‘With continued lack of sufficient sleep, the part of the brain that controls language, memory, planning and sense of time is severely affected… 17 hours of sustained wakefulness leads to a decrease in performance equivalent to a blood alcohol level of 0.05% (two glasses of wine)’ (BBC).
Prolonged absence of sleep will begin to take its toll in more physical/bodily manners. Think: hormonal imbalance and emotional outbursts, as well as fatigue in the limbs and muscles, seeing as the body isn’t getting the much needed downtime required to repair itself.
What actually happens when we sleep?
The most prominent image for what happens when we sleep, is of the brain ridding itself of garbage. Throughout our every-day lives, the brain is constantly forming new connections, cataloguing new experiences and forming new memories. Scientists believe that the act of actually putting ourselves to sleep, and taking the focus off of physical activities, allows the brain to purge itself of useless or trivial connections, memories and so forth, freshening up our mental space for the next day.
Interestingly Maiken Nedergaard, head of a study done by the University of Rochester, found that the spaces between brain cells of sleeping mice actually reduced in size, meaning that everything basically ‘flows’ quicker – this also applies to the earlier idea that we flush out the useless toxins and ‘garbage’ collected throughout the day.
This physical change is a sign of ‘brain plasticity’, another theory about the reason for sleep. Brain plasticity plays an important role in the lives of children, especially, as it’s essentially a visual sign of brain development. Yet more interesting is that this phenomenon continues on into adulthood, which separates it from traditional kinds of bodily growth.
Why do we sleep? Is it to dream?
If we want to get into the truly philosophical, abstract territory of sleeping – we need to take a look at dreaming, and what it means. But beware: dreams are where Carl Jung, David Lynch and Katy Perry have made their living.
Dreams occur most heavily during the rapid eye movement period of sleep (REM) – which usually happens somewhere around 60 – 90 minutes after falling asleep. During this time, our brains are still live and kicking, which prompts some physical reactions from the rest of the body – roving eyes, heavier breathing, and increased heart rate – in response.
In ancient times, people believed dreams were epiphanies or messages from angels. But now, in our enlightened 2023, we think of them more as the mind remembering things that have happened recently, or wrestling with big issues that haunt us, subconsciously. This is why many dreams can leave you feeling like an emotional wreck, or excited, or terrified. Often it may be because you’ve been facing something that you’ve been hiding from. All from the comfort of your bed.
So could dreaming be the answer? Just like physical repairs, does sleep help with mental repairs, where we try to resolve things troubling us? It’s difficult to say. Even in today’s scientific climate, where we’re approaching legitimate artificial intelligence as each day passes, we still aren’t 100% sure why we sleep, or why it takes up so much of our time.
But it’s certainly fun to speculate.