Deep sleep is the most important stage of sleep that we go through each night as it’s vital for our bodies to rest and recuperate.
Human beings experience two different types of sleep in one cycle: Non-REM (Non-Rapid Eye Movement) and REM sleep. The first is the one you experience when you first fall asleep and this is when deep sleep happens as your body and brain slows down. While the second normally takes place in the latter half of the cycle and is characterised by vivid dreams and rapid eye movements behind closed lids.
It’s this first type, the deep dozing, that’s so important for us. A lack of sleep can affect the body very seriously, leaving us tired all the time and struggling to wake up properly in the morning. So how much deep sleep do you really need per night? Here, leading sleep experts 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 as this is when we are least likely to wake up early 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 James Wilson, a sleep behaviour and environment expert known as The Sleep Geek.
“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.”
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, 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 and heavy snoring occurs. That is why those that suffer from the condition don’t know or remember doing it.
How much Deep Sleep do you need?
A quarter of our sleep time equates to deep sleep, which is 90 minutes a night. Although generally if you can get more than an hour and a half that would be beneficial.
“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 adults aim for about 6-9 hours sleep a night and so based on this, James encourages just over 90 minutes of slow wave sleep everyday.
“Everyone is different when it comes to working out how much deep sleep we need,” says Sleep Geek James. “A good eternal rule is that about 20% of your total sleep time should be made up of deep sleep.”
Research suggests that getting the right amount of slow wave sleep could help fight-off brain diseases like Alzheimer’s. One study showed that high levels of cerebrospinal fluid (CSF) was detected during deep sleep. And this flushes out toxins, helping your brain stay healthy. Whilst another study 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
There are a number of bad bedtime habits which can affect our quality of kip. If you’re struggling to get enough deep sleep, you should definitely start by addressing these things.
“There is some research to show napping can worsen the quality of slow wave sleep,” says James. “And eating too close to bedtime raises our core temperature and can impact the quality of our sleep.”
Avoid eating too close to bedtime, he says, as this “raises our core temperature and can impact the quality of our sleep.”
“Winding down properly before bed, focusing on activities that drop our heart rate and allows us to relax helps. As does having a warm bath or shower to drop our core temperature and make us cooler.”
Expert Wayne agrees that a warm bath will set you up for a better snooze too. He also suggests avoiding certain foods before bed and opting for a low-carbohydrate diet. As one study from the University of Sydney demonstrated, the low-carb diet known as the Ketogenic diet actually increased slow wave sleep in participants monitored.
Further research has revealed that exercise plays a part in increased sleep quality too. One study in the Sports Medicine Journal showed that exercising in the evening improved slow wave sleep. And another study from the University of South Carolina found the same results when the majority of people exercised after 8pm.
But sometimes, it’s best to just go with the flow. As Wayne says, sometimes 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.”