Why Do We Sleep?

To answer this question, let’s first ask ourselves:

Why do people not sleep?

People usually sacrifice their sleep because they believe it is not important enough — a waste of time, so to speak, that could be used towards more productive activities. Most believe that sleep is simply a time where our mind and body turns off. This, however, is widely incorrect.

We spend almost a third (36%) of our lives asleep, which would suggest that sleep is a necessary process required for our biology. However, two thirds of adults, across nations, fail to obtain the recommended 8 hours of sleep (as recommended by WHO and the National Sleep Foundation).

Matthew Walker, an expert researcher on sleep and its impact on humans, has suggested that society’s lack of concern towards sleep has been caused by the historic failure to explain why we need it. Minds such as Francis Crick and Sigmund Freud have all attempted, and failed, to explain sleep’s obscure code. Until recently, scientists were not able to provide a complete answer to why we sleep.

From an evolutionary perspective, sleep would appear to be a foolish biological phenomena. Whilst sleeping, you are unable to undertake the main 3 basic drives in life — gathering food and drink, socialising, and reproducing.

“If sleep does not serve an absolute vital function, it is the biggest mistake the evolutionary process has ever made” — Dr Allan Rechtschaffen.

That being said, sleep still persisted. Every species sleeps.

Thus, “Why Do We Sleep?” is perhaps the wrong question to ask. This question implies that there is a single function to sleep. Theories have ranged from the peculiar (eyeball oxygenation), the logical (conserving energy) and the psychoanalytic (a non-consious state in which we fulfil repressed wishes).

However, as Matthew Walker explains in his book ‘Why We Sleep’, sleep is infinitely more complex.

We sleep for a range of functions. Whilst we sleep, our brain and bodies endure an active period in which processing, restoration, and strengthening occurs.


  • Certain brain areas become active when sleep (more so than when we’re awake). Evidence suggests that these areas are associated to restoration and metabolic pathways — thus providing good support for the restoration hypothesis.

  • Sleep also helps with our psychological health. Sleep helps recalibrate our emotional brain circuits that allows us to navigate next-day social and psychological challenges with a cool composure.

  • Memory consolidation — Evidence suggests that sleep depriving an individual after they have learnt a task will almost always inhibit and attenuate their ability to have effectively learnt that task.

  • Creativity — Sleep enhances our ability to come up with novel solutions to complex problems (3x advantage).



  • In our bodies, sleep restocks our immune system to help fight malignancy, prevent infection, and fight off sickness.

  • Sleep balances insulin and circulates glucose in order to restore the metabolic state of the body.

  • Sleep also helps control our body weight (via healthy food selection vs. impulsivity), which regulates our appetite.

  • Sleep maintains flourishing microbiome within the gut, which is somewhere we know is an area where a large quantity of our nutritional health begins.

  • Sleep is also linked to the fitness of our cardiovascular system — lowers blood pressure whilst ensuring our hearts are in good condition.

There is not an organ in our bodies or a process within the brain that is not enhanced by sleep (and impaired when we fail to get enough sleep). The physical and mental impairments caused by a bad nights sleep are worse than those caused by an equivalent absence of food or exercise. Given this, one might question whether there are any biological functions that do not benefit from a good nights sleep. Research would suggest, no.

Based on this, we can conclude that sleep is a fundamental process that resets our brain and body health every day.

Sleep is not an indulgence. Its a necessity.

Watch this brilliant TED talk given by Professor Russell Foster to gain a more detailed understanding of why we sleep and how it can impact us as humans…

Video from youtube.com


Having gained a good understanding of the fundamentals regarding why we sleep, here are 3 tips to try out yourselves the next time you want to achieve a healthy nights sleep…

  1. …go to bed and wake up at the same time every day.

  2. …relax at least 1 hour before bed (e.g. read a book).

  3. …make sure your bedroom is dark and quiet (e.g. use blinds, an eye mask or ear plugs).

Click here to read our next blog that discusses the architecture of sleep in more detail, and provides another 3 useful tips you can use yourself to help improve your sleep.

Umer Nawaz