Before we answer the question why we need sleep, lets first define what sleep actually is. So what is sleep? The Oxford English Dictionary defines sleep as:

“a regularly recurring condition of body and mind in which the nervous system is inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended”

So basically, it’s a state we enter where the body shuts down and we slowly drift out of consciousness.

When you put it in terms like that, it seems like a very weird thing to happen. Imagine explaining this to an alien who had never heard of sleep before: “Well, every night we go to our own special places where we shut down and lose consciousness and then automatically get turned back on when it’s morning.”

Sleep is a very strange thing indeed, but why do we need sleep? And why can some people get by on much less sleep than others?

Do we actually need sleep?

So do we need this sleep? One way to find out is to see how we cope without it. If we don’t get enough sleep, we start feeling the effects of sleep deprivation. These effects get progressively worse until we do get some sleep. Our health dramatically declines and our bodies eventually force us to sleep (whether we want to or not).

If for some medical reason we lose the ability to sleep, we die. We unfortunately know this because the extremely rare sleep disorder Fatal Familial Insomnia which causes people to slowly lose the ability to sleep. Their bodies shut down, their brain deteriorates  and eventually they die from severe sleep deprivation.

So the simple answer to whether we need sleep is yes, we do. We need sleep to function, and without it, we couldn’t live. But different people need different amounts.

Why do some people need more sleep than others?

The amount we sleep changes with age. Newborns need the most sleep. In fact they spend the most of the day sleeping, up to 18 hours. The required number of hours required for sleep gradually fades until we reach adulthood, where it stays at around 7 – 8 hours of sleep per night.  These numbers are averages. Some people only need 4 – 5 hours sleep per night to feel fully refreshed.

But why do some people need more sleep than others? We all have the same biology, so shouldn’t we all need the same amount of sleep?

Time spent asleep vs. sleep quality

The amount of time you sleep doesn’t really mean much. What really matters is the quality of sleep you get. Even if you sleep a full 9 hours, if you don’t enter into good quality deep sleep during that time, you’ll feel like you’ve been awake all night.

So someone who sleeps for just 6 hours a night might actually get more sleep than someone who sleeps 9 hours simply because their sleep quality is better.

You can improve your sleep quality by:

• Sleeping in a comfortable sleep environment
• Going to bed and waking up at around the same time each day
• Relaxing before bed to reduce stress and anxiety
• Avoiding alcohol, caffeine, nicotine, heavy exercise and bright light before bed

Some sleep patterns aim to improve what’s called sleep efficiency, which is the quality of sleep you receive vs. the amount of time spent sleeping. So the higher your sleep efficiency, the less time you’ll need to sleep to wake fully refreshed. Some polyphasic sleep patterns (multiple sleep and wake times) require just 3 hours of sleep per day, simply because you spend more time in the deeper more refreshing stages of sleep and less in the lighter stages, increasing the quality of sleep.

So simply put, the better the quality of your sleep the less time you’ll need to spend sleeping.

The Need For Sleep and Genetics

While some people need around 6-8 hours of good quality sleep per night, there are those who can sleep less than 6 hours a night and still feel bright and alert in the morning. These people are called short sleepers.

Famous short sleepers include:

• Napoleon – 4 hours per night
• Bill Clinton – 5 to 6 hours per night
• Thomas Edison – 3 to 4 hours per night

It’s estimated that only around 1-3% of the population are short sleepers. Far fewer than the 33% of sleep deprived Americans who try to get by on this level of sleep.

The reason why these people need so little sleep is down to their DNA. Researchers found that a rare gene variation known as hDEC2 is responsible for reducing the need of sleep. By modifying this gene, scientists have been able to turn normal mice into short sleepers. Maybe one day they could do the same for humans.

Would needing less sleep be a good thing?

Just because we could genetically reduce our need for sleep, does it mean that we should? Ignoring the ethics of doing so, would not needing as much sleep be advantageous?

Reducing our sleep by 2 hours a day gives us an extra 30 days over the course of a year. And if we could eradicate our need for sleep altogether, that’s an extra third of our lives that can be spent doing something other than sleeping.

But sleep doesn’t just fulfil a need to be inactive, a lot happens when we sleep. The complete picture as to exactly why we sleep is still a bit of a mystery. Among many things, sleep boosts our immune system, repairs the body and helps us learn new skills. Sleep comes with a number of benefits.

But research into short sleepers show that short sleepers tend to have fewer weight problems, have better moods and have very high energy levels. Although only very few short sleepers have been studied by scientists because there are so few of them, so we can’t come to the conclusion that all short sleepers are like this.

But at least for the time being, we all need sleep. Until scientists can find a way to wipe it out from our DNA, we may as well make the most of it. By improving our sleep habits, sleep environment and sticking to a regular sleep pattern, we can all get the deep refreshing sleep we need.