How much deep sleep do you need and how to get more of it

We've asked the experts to explain deep sleep and what to do if you want more of it

A woman sleeping in bed to illustrate how much deep sleep do you need
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It’s the most important stage of sleep that we go through each night, but how much deep sleep do you need?

A lack of sleep can affect the body (opens in new tab) very seriously, leaving us wondering why we’re tired all the time (opens in new tab) and struggling to wake up properly in the morning. While REM sleep is characterised by vivid dreams (opens in new tab) and rapid eye movements behind closed lids, it’s the non-REM sleep where you’re sleeping deeply and the brain slows down.

“Everyone is different when it comes to working out how much deep sleep we need, but a good eternal rule is that about 20% of your total sleep time should be made up of deep sleep.” says James Wilson (opens in new tab), a sleep behaviour and environment expert known as The Sleep Geek. We've asked him and other leading sleep experts to share their knowledge and top tips on how to achieve more deep sleep each night.

What is Deep Sleep?

Deep Sleep is a period of sleep that takes place before dreaming. It is called deep sleep because this is when we are least likely to wake up early (opens in new tab) and are often enjoying our deepest slumber. 

“Deep Sleep is a stage of sleep that we move into after about 20-25 minutes of falling asleep, and it is very important to our physical recovery,” says Sleep Geek James.

“It is when growth hormone is released and where our organs, muscles and cells repair,” he adds, “and it’s where the process of consolidating memory starts and where our body releases chemicals that boost your immune system (opens in new tab).”

The restorative process that takes place during deep sleep is often what makes us feel like we’ve had a good night’s rest in the morning. 

“Unlike Rapid Eye Movement (REM) sleep, deep sleep is when the brain waves slow down,” says Wayne Ross (opens in new tab), a sleep researcher and advisor at InsideBedroom. This type of sleep is also often referred to as Slow Wave Sleep (SWS). 

“It is difficult to wake from slow wave sleep, and when we do wake it takes a while to realise or become fully aware of our surroundings and situations.”

It is during deep sleep that sleepwalking (opens in new tab) and heavy snoring occurs, and is why those that suffer from the condition don't know or remember doing it.

How much Deep Sleep do you need?

“It is advisable for an adult to get 1 to 3 hours of deep sleep per 8 hours of nightly sleep each night,” says Sleep Geek James. This amount is key to feeling rested, staying healthy and waking up happy.

The NHS recommends (opens in new tab) adults aim for about 6-9 hours sleep a night and, based on this, James encourages just over 90 minutes of slow wave sleep everyday. 

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Research suggests that getting the right amount of slow wave sleep could help fight-off brain diseases like Alzheimer’s, and one study (opens in new tab) from Boston University showed that high levels of cerebrospinal fluid (CSF) was detected during deep sleep, and that this flushes out toxins, helping your brain stay healthy. 

Another study (opens in new tab) published in the journal of Sleep Medicine Clinics (opens in new tab) revealed that slow wave sleep decreases in old age, so it’s wise to take steps to improve the quality you have as soon as you can.

How to increase your amount of deep sleep

Stop napping during the day

According to Sleep Foundation (opens in new tab), napping later in the day can have a negative effect on the amount of deep sleep you will get. 

They say: “If you nap in the morning, the sleep consists primarily of light non-rapid eye movement (and possibly REM) sleep. In contrast, napping later in the evening, as your sleep drive increases, will comprise more deep sleep. This, in turn, may disrupt your ability to fall asleep at night. Therefore, napping late in the day is discouraged.”

They add that - based on various studies - around 10 minutes is considered the best nap duration, because it allows you to catch a quick rest without entering slow-wave sleep and feeling groggy afterwards.

Avoid eating too close to bedtime

"Eating too close to bedtime raises our core temperature and can impact the quality of our sleep," says James, while Wayne suggests avoiding certain foods before bed (opens in new tab) and opting for a low-carbohydrate diet (opens in new tab)

A study from the University of Sydney (opens in new tab) found that the low-carb diet known as the Ketogenic diet (opens in new tab) actually increased slow wave sleep in participants monitored.

Try a hot bath before bed

“Winding down properly before bed, focusing on activities that drop our heart rate and allow us to relax helps,” says James. “As does having a warm bath or shower to drop our core temperature and make us cooler."

A report published in Sleep Medicine Reviews (opens in new tab) found that having a 40 to 43°C bath one to two hours before bed helped participants get the best quality sleep, and also found that bathing at that time and temperature helped people fall asleep an average of 10 minutes quicker than normal. 

Exercise in the evening

A study from the University of South Carolina (opens in new tab) found that survey respondents who exercised after 8pm fell asleep more quickly (65%), had deeper sleep (62%), and woke up feeling better (60%). In another study, published in Scientific Reports (opens in new tab), it was also found that exercise improves the quality of slow wave sleep, so consider switching your morning workout to later in the day, if you can.

With all that said sometimes, it's best to just go with the flow. As Wayne says, the best thing you can do is not overthink it. “It is known that the more you force yourself to sleep, the poorer the sleep quality upon awakening. Just sleep when you can.”

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