Why do we need sleep?

Why do we need sleep?

It’s interesting that we spend about a third of our lives sleeping, yet no one, not even all those clever doctors and medical students at Harvard Medical School, can tell us exactly why we sleep. All we know for certain is that we need to rest. In fact, every living creature from cats and pigs to grandparents and kids, must sleep to function properly. And, like eating, breathing and drinking water, sleep is necessary for us to function and survive.

When we sleep, we’re giving our body a chance to relax - which means a good nights sleep relies on a good sales mattress. Kind of like a very quick holiday. It’s also a chance for our brain to rest and get organised. While scientists aren’t exactly sure what our brain is organising or how it’s organising or even why it’s organising, they believe it might be the time when the brains sorts and stores information, solves problems and replaces chemicals. Here are 5 possible reasons why we sleep in a bit more detail:

#1: To cleanse our memory

Remember the ‘Pensieve’ in the Harry Potter books? It was a place where Professor Dumbledore could store important memories because there were so many in his brain and he was worried he’d forget them. Obviously we can’t pick up our wands and take memories out of our brain to store in a ‘Pensieve’. Instead, some sleep scientists believe, we sleep. These scientists believe that the main purpose of sleep is so our brain can prune back the memories we don’t need, so we don’t overload our brain with irrelevant memories. This helps us remember the relevant ones1.


#2: To rejuvenate our body

Another theory for why we sleep is so our body can restore what’s lost while we’re awake. There’s been quite a bit of research2 to prove that major restorative functions, including tissue repair, muscle growth and growth hormone release, mostly occur, or some cases only occur, while we sleep. So if your child gets out of bed and they look bigger or taller, chances are they grew in their sleep!



This theory suggests that we sleep so our brain can rest and clean out built-up adenosine. While we’re awake, neurons in our brain produce this by-product as a result of all our brain cells’ activities. Some scientists believe that when adenosine builds up in our brain, we begin to feel tired2. As more builds up, the more we need to sleep. As soon as we’re asleep, the adenosine in cleaned out, so when we wake up we feel more refreshed and awake.


According to some sleep scientists, we sleep so we can maintain normal levels of cognitive skills3. This includes things such as speech and memory as well as our ability to think. Without enough sleep, we start to feel grumpy, irritable, forgetful and groggy. In fact, after just one night without sleeping, humans find it hard to concentrate and our attention span is much shorter. Research also shows that if we don’t get enough sleep, it’s difficult, and sometimes impossible, to respond to changing situations or to make good judgment calls. This can be disastrous in situations such as driving where sleep deprivation could prove to be fatal.

Some sleep experts believe that dreaming is another way for our brain to clean out bad memories.



There is a thought that while we sleep to rest, refresh and flush out bad chemicals from our brain, we also sleep so we can dream. But why do we dream? That’s another good question. While there are many studies, no one is really sure what they accomplish. However, some sleep experts believe that dreaming is another way for our brain to clean out bad memories while other researches think dreams help the brain get organised and store important psychological information that’s been learnt during awake time4.


So what would happen if you didn’t sleep?

After 1 night: We become irritable, clumsy and cranky.

After 2 nights: We have trouble doing things like thinking and simple tasks such as talking and walking.

After 5 nights: We start to hallucinate.

Eventually, further sleep deprivation means that it becomes impossible for our brain to give its directions to the rest of our body.

So it’s important to get a good night’s sleep every night if you want to stay focused and function well. If you’d like to discuss your bed or mattress needs, visit your local Snooze store. After all, it’s amazing what a little Snooze can do!



  1.  ABC Science
  2.  Harvard Medical School
  3.  BBC Science
  4.  NBC News
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