Deep Sleep: What It Is & Why It’s Important
5 min read
Last Modified 31 August 2023 First Added 23 April 2019
Deep sleep definition:
Deep sleep is the stage of sleep you need to feel refreshed when you wake up in the morning. Unlike rapid eye movement (REM) sleep, deep sleep is when your body and brain waves slow down.
Deep sleep, also known as slow wave sleep, is a stage of NREM (non-rapid eye movement) sleep which usually occurs during the third stage of your sleep cycle. During this sleep stage your body is at its most relaxed and won’t wake easily, even from loud noises. If you do wake during this sleep, you may feel groggy or tired.
During deep sleep you experience certain physiological changes including:
It occurs for longer periods during the first half of your sleep and the longest period of deep sleep will happen quite soon after you fall asleep. This stage can last from 45 to 90 minutes but will get shorter during each sleep cycle until eventually it stops.
This sleep is the most restorative sleep stage. During this period, our bodies work to repair and grow, meaning it’s important for recovery. This stage of our sleep is also when energy is restored. So, if you find yourself waking up still feeling tired of a morning, it’s likely you’ve not had enough of it.
According to Healthline:
‘Deep sleep is also when the pituitary gland secretes important hormones, like human growth hormone, leading to growth and development of the body.’
This stage of sleep is when most of our energy restoration, cell regeneration and tissue repair happen. The blood that’s not used in the resting brain is sent to your muscles, helping to heal not only muscular issues but also immune and nervous system problems.
Read more about this process: How To Sleep After Exercise To Aid Muscle Recovery & Growth
As well as physiological benefits, it is also the point in your sleep cycle where you process information. A lack of it means your brain can’t convert information you’ve received throughout the day into memory. That’s why cramming for an exam the night before rarely works!
Deeper sleep is, therefore, extremely important for both your physical and mental health and not getting enough has been linked to health problems later in life. A recent study by the Washington University School of Medicine in St. Louis found that adults who do not get enough deep sleep have higher levels of a brain protein called tau which is linked to Alzheimer’s disease.
Furthermore, the NHS warns that ‘regular poor sleep puts you at risk of serious medical conditions, including obesity, heart disease and diabetes – and it shortens your life expectancy’.
Around 13-23 percent of your sleep should be made up of deep sleep. Your sleep is made up of non-REM sleep (75%) and REM sleep (25%) with deep sleep accounting for some of the non-REM portion.
It is responsible for repair and growth in the brain and body, younger people tend to need more of it. It’s common for babies and children to need 2-3 hours of deep sleep each night, while teenagers and young adults may only need 1-2 hours according to New Health Advisor. Pensioners and older people often need significantly less sleep overall.
The best and easiest way to accurately track how much deep sleep you get is by using a fitness or sleep tracker. These use your heart rate and movements to build an account of how long you spend in each sleep stage and can also show you what the average person of your age and gender should be getting.
Another way to gauge whether you’re lacking is by how tired you feel the next day. If you’re more tired than usual or consistently tired, the chances are you’re not getting enough.
There is no singular way to increase the amount you get. However, improving the quality of your sleep overall and the amount of sleep you get can help.
The short answer here is no. Deep sleep has been linked to sleepwalking, night terrors, bedwetting and sleep eating. However, it doesn’t cause these problems – they just happen to occur during this sleep stage.
Related – How To Avoid Nightmares
Most of these problems are caused due to stresses and anxieties which a person is suffering from while they are awake. If you are suffering with a sleep disorder or struggling to sleep, visit your GP for more advice.