Why Do We Sleep?

man eyes closed wearing eyeglasses

Although we spend over a third or more of our lives sleeping, we still have no concrete idea as to why. Scientists have spent countless decades investigating the effects of sleep deprivation, sleeping disorders and cures for these disorders, such as insomnia, however the question of why we sleep is still one of the greatest mysteries.

Sleep is technically a vulnerable state seemingly at odds with our need to nourish ourselves and propagate. It finds us in a state of reduced responsiveness, reduced motor activity and reduced metabolism and therefore it is assumed that it must be necessary for a universal, but as yet, an entirely unknown and vital function.

There are also questions raised as to how despite being in a deep sleep, we can wake up at the slightest of noises. We might hear a tap dripping or a baby whimpering, but remain entirely unaware of a giant thunderstorm thrashing about outside our bedroom window.

Sleep is so important to our daily functioning that millions is spent on research into sleep disorders, including causes, treatments and the use of natural sleep remedies. If you are one of the millions of people who suffer insomnia, see natural cures for insomnia.

Why do we sleep?

There are various theories as to why we sleep:

  • Freud and Jung believed that dreams are the way that our subconscious mind communicates with our conscious mind. Therefore by analyzing dreams we are able to solve day to day problems and issues in our lives
  • Modern scientists suggest that sleep is important for the brain’s ability to process and consolidate memories from the previous day. By the same token, it can help clear unnecessary memories and free up “disk space”, so to speak, for more neural connections to occur
  • There is also the theory that sleep helps to return the body to homeostasis and to repair any damage done to the body and the brain during the previous day. Its like a “top up” effect, bringing us back into balance on a daily basis
  • Last year UCLA neuroscientist Jerome Siegel proposed that sleep helps to optimize the timing and duration of day time activities by conserving (and thus recharging) energy

All theories are valid as they are interesting, yet none are definitive.

What we do know about the function of sleep

There are many things we know about the function of sleep, at least in terms of what happens if we don’t get enough of it:

  • Sleep is critical for anti aging as our cells do the biggest repair job while we are sleeping. Less sleep means we age faster (and less gracefully!)
  • Lack of sleep causes a decrease in keratin and collagen. Keratin is a protein important for strong skin, hair, nails and teeth. Collagen, also a protein, connects and supports body tissues such as skin, bone, muscles, tendons and cartilage
  • Growth hormones are secreted at night and they repair the body’s tissues and encourage skin to grow but only after 6 hrs and optimally after 8 hours
  • Our responsiveness deteriorates after 18 hrs without sleep. At this stage our reaction times slow from a quarter second to half a second. We start to experience bouts of micro sleep where we zone out for anything between 2-20 seconds at a time. At 20 hrs without sleep our responsiveness slows to the same rate as someone with 0.08 blood alcohol
  • Sleep deprivation affects our concentration and effectiveness and makes us irritable, nervous, sleepy, tired and exhausted. It also creates aches and pains that aren’t usually there. See effects of sleep deprivation

Sleep is an adaptive state that maximizes the efficiency of all activities

While some people can get by on 4 hrs sleep a day, others may need upwards of 10 hrs plus for optimum functioning. The understanding of the importance of sleep keeps sleep disorders, research for remedies and use of natural sleep remedies high on the agenda.


Miller, Max Why do we sleep, Big Think

Gorman, Christin, Why we sleep, Times Online

Siegel, James, 2009, Nature Sleep viewed as a state of adaptive inactivity.

Grant, Suzi, Alternative Ageing, Penguin Books, London