How much deep sleep do you need?

The average adult needs between 1 – 1.5 hours of deep sleep every night, approximately 15-21% of a 7-hour sleep. The first and longest deep sleep stage is experienced within the first hour of sleep and lasts 20-40 minutes. Caffeine, fatty foods, alcohol, pain and sleep medication can all affect how much deep sleep you get.

What is deep sleep & how long does it last?

In normal sleep, we pass through stages of light and deep sleep, alternating between them throughout the night. This is known as our sleep cycle. We dream during the part of the light sleep stage known as REM. These lighter stages of sleep allow us some awareness, to hear when the baby crying or to get up if our bladder is threatening to wet the bed.
Deep sleep is the heavy, restorative, blackout part of the night's shuteye, when it would take a small earthquake, or an extremely shrill child, to bring us back to groggy consciousness. Ideally, a person should get approximately 1 – 1.5 hours of deep sleep every night (that's roughly 15-21% of our total sleep time if we sleep 7 hours).(1)
We tend to have long deep sleep stages at the start of the night. The longest is reached within the first hour of sleep and lasts 20-40 minutes. These rotations of deep sleep get shorter in length as the night progresses. Towards morning, just before we wake, we are more likely to be sleeping quite lightly and having nice long REM dreams.

Why is deep sleep important?

Deep sleep is when young people grow. During the early part of the night, in deep sleep, growth hormones are produced.(2) All the more reason to boot those kiddies up to bed early on a school night.
The brain undergoes a cleaning process during deep sleep when spinal fluid washes over it driven by brain waves, specifically slow wave activity.(3) I would love a visual of this, it's called glymphatic clearance. It's thought to play a role in preventing diseases, such as dementia and Alzheimer's, linked to a build-up of protein that can happen during sleep deprivation.(4)
During deep sleep, brain waves known as sleep spindles occur. These are short intense bursts of activity during which all the senses are shut down and new memories or motor skills (such as typing or a new dance step) are implanted in the brain.(5) It's as if the brain is downloading new software or reconfiguring the system necessary for concentration and memory.
Deep sleep is vital for the correct function of the immune system which uses inflammatory signallers known as cytokines and TNF-alpha to fight infections that may come our way.(6) However, if they are left unchecked, such as when we are sleep-deprived, they can go overboard with inflammation that can lead to joint pain and conditions such as diabetes. A well-rested immune system will in turn play a role in regulating sleep. A good example of this, the immune system and our sleep working together, is the extra sleep we get when we are fighting off a cold or flu infection.
ATP (adenosine triphosphate) is like our battery pack. It's a molecule that stores the energy that is made when we break down and process the food that we eat. During deep sleep when the brain is quiet, ATP surges occur and it's thought that this is how energy is replenished, especially in the brain. Ergo, deep sleep could be said to be like charging your battery.(7)
It's still not clear if it is during deep sleep or just sleep in general when the body gets the opportunity to repair sore, tired muscles, and any wear and tear to the nervous system or tissues that may have occurred. However, we naturally get less deep sleep in old age when repair and recovery tend to take longer.

What disrupts deep sleep specifically?

It makes sense to consider all the usual culprits like caffeine, alcohol, inactivity and a lack of natural light in the mornings when we are looking where to cast the blame for any insomnia or poor sleep quality. Research-wise, the following have been found to specifically disrupt deep sleep.

The wrong body temperature – We need our skin to feel warmth in the hour before we get to sleep, ironically because this triggers the body-cooling response that is necessary for the slow brain waves we experience during deep sleep.(8)(9)
Too many stodgy and fatty foods (such as chips, buttery white bread and creamy pasta) and not enough fibre is associated with less deep sleep.(10)
Pain and sleep medication, such as barbiturates and opioids, can disrupt sleep architecture, and the correct balance of sleep stages such as deep sleep and REM.(11)(12)

Tips for increasing time spent in deep sleep.

Get nice and cosy that hour before bed.

Snuggle into your fleecy pjs, have a warm bath, and embrace your teddy hot water bottle. Warming the skin before bed will help the body to ultimately cool the core temperature needed for deep sleep. It's also helpful to keep the bedroom at a reasonably cool temperature help prevent the body overheating during the night. During perimenopause and menopause, the body's ability to regulate the inner thermostat goes out the window as oestrogen levels fall. Menoforce Sage tablets may help relieve the symptoms of hot flushes and night sweats that can disturb sleep. Keep a cold glass of water next to the bed to drink when you are hot or thirsty.

Download a relaxing soundtrack.

Certain music, noises or frequencies that promote delta brain waves that happen during deep sleep can help improve sleep .(13) One of these is pink noise, which sounds like a constant static hum, supposedly suggesting comforting sounds like rainfall on autumn leaves. You can find an example on YouTube.

Try a natural sleep remedy

Try a natural herbal sleep remedy such as Dormeasan Sleep. 30 drops in a little fruit juice can be taken before bed, or during the night if you wake, to promote restful sleep. Alternatively, a nice cup of herbal tea such as chamomile or lemon balm may do the trick.

Essential oils can be a lovely addition to a bedtime routine. A few drops of Lavender, Bergamot or Sandalwood oil may create a relaxing and soothing olfactory atmosphere in the bedroom.

Watch what you eat.

Although a low fibre diet is associated with less deep sleep, there's also a bit of evidence that carbohydrates may help you get to sleep; so the answer is probably to aim for a balanced diet that includes enough lean protein, plenty of vegetables, and some whole grains: brown bread, oats, brown pasta and brown rice. Some foods are particularly at promoting sleep, such as tart cherries and kiwi fruit .(14)

My Top Tip:

Take 30 drops in a little juice or water 30 minutes before bedtime. Helps to restore natural sleep using fresh herbal extracts

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How much deep sleep do you need?