The Benefit of a Good Night’s Sleep
Of all the things you can do to stay healthy, sleep is up there as one of the most important. When your conscious brain switches off, your body gets to work. Muscles, tissues, and cells begin to repair themselves — and your immune system is strengthened, too. And while you snooze, your brain consolidates the neural pathways that you built when learning new things throughout the day.
That’s why you feel so fresh on the other side. Because during the night, you’re healing.
Yet, it’s not like that for everyone. If you sleep too little, or you have low-quality sleep, you might not feel well-rested at all. For that, you need to pass through all of the stages of the sleep cycle – from light sleep to deep sleep and to REM.
Here, though, we’re going to look at one stage of sleep in particular: that’s deep sleep. It’s one of the most important of the different stages of sleep – the one that helps your body repair physically. But how much deep sleep do you need? Let’s find out.
The Stages of Sleep
To understand deep sleep, you need to get to grips with the different stages of sleep in general.
These, over the years, have been categorised differently. So, while you might see people refer to rapid eye movement (REM) sleep and non-rapid eye movement (or NREM or non-REM) sleep, we’ll use the more modern classification.
Scientists have found 5 distinct stages of sleep – often described as 0-4.
Awake Time. The first stage – or ‘zero’ stage – is awake time. Right now, you’re in awake time. But you’ll also pass through this stage during the night when you are in your lightest sleep.
Light Sleep. Stages 1 and 2 are both light sleep. The first stage doesn’t last long: about 5 minutes. This is when you doze off. However, you can spend as much as half of the night in stage 2. Here your body temperature drops and your heart rate and breathing slow down. In these lighter stages, you can be woken up reasonably easily.
Deep Sleep. Here it is. Known sometimes as delta sleep or slow-wave sleep, this is when you’re in full repair mode. Brain activity slows and it’s quite difficult to be woken up. More on this below.
REM Sleep. Probably the most well-known of the sleep stages, stage 4 is REM. Your dreams become very vivid, but you become physically immobile. And your brain is busy working on strengthening memory and learning.
Overall, scientists reckon that you pass through this cycle 4 or 5 times every night – with each cycle lasting roughly 70 to 120 minutes in total.
Deep Sleep in Detail
What about deep sleep, then? This particular stage of sleep is thought to last for about 20 to 40 minutes in each cycle. It’s the famous time when it’s hard to wake up, and, if you are woken, you tend to feel pretty groggy.
That’s because, during deep sleep, your brain waves become slower and deeper. Although scientists are not 100% sure what happens during deep sleep, it’s thought to be the moment when your brain rests and when your body does the most to repair itself physically.
Why We Need Deep Sleep
Here are some of the things that we think happen during deep sleep. While so many things are still uncertain, it’s thought that deep sleep’s real magic happens in the earliest cycles of sleep. That means lie-ins are much less effective than an early night for feeling fresh the next day.
- Human growth hormone release. Primarily in a night’s first sleep cycle, human growth hormone (HGH) is released during deep sleep, according to scientists. In children, this encourages growth – but in adults, it regulates fat and muscle, bone density and brain function. It also helps your body to repair and restore your cells.
- Immune system boost. Deep sleep is the period when our metabolism is lowest. As a result, energy can be used instead to fight infection. That’s why you sleep more deeply when you’re unwell.
- Memory consolidation. REM sleep primarily is when your brain is restored. However, during deep sleep, it’s believed that short-term memories that were formed during the day are transferred to the part of the brain responsible for long-term memory. While deep sleep is better known for being beneficial for your physical body, this process also makes it crucial for learning.
How Much Deep Sleep Do I Need?
As we’ve mentioned, during each cycle of sleep, you will normally have between 20 and 40 minutes of deep sleep. That means that a normal total amount of deep sleep per night is around 2 hours. This is primarily what you should be aiming for.
You should manage this if you get 7 to 9 hours of restful sleep a night. However, if your sleep is regularly interrupted, or if you suffer any kind of sleep disorders, it will be your deeper sleep that suffers.
If you don’t get enough deep sleep, you can experience all sorts of nasty health problems. Type-2 diabetes, for example, can be caused by a lack of deep sleep, while your memory, concentration, and mood can suffer too. In more chronic cases of sleep deprivation, Alzheimer’s and heart diseases are also possible consequences.
How to Get More Deep Sleep
The best thing to do to get more deep sleep is to increase your total sleep time. If you feel like you’re low on deep sleep, it’s probably because you’re not getting enough sleep overall. As we said, those of us who sleep for 7 to 9 hours will probably have enough deep sleep to be healthy.
However, it may be that the amount of time asleep is not the problem. If the quality of your sleep is inadequate, your deep sleep will suffer too. Here are some things that can help:
Cut down on alcohol. Alcohol can help you fall asleep, but it will negatively affect the quality of sleep. That’s because it messes with your sleep cycle and circadian rhythms. It’s primarily REM sleep that alcohol damages though, as it tends to throw you immediately into a deep sleep – and wakes you up repeatedly during the night.
And cut down on caffeine, too. Caffeine has the opposite effect. It makes it harder to fall asleep and makes it more difficult to enter deep sleep – while it doesn’t seem to affect REM. Try to avoid caffeine at least six hours before bedtime.
Exercise. While exercising a couple of hours before bedtime can have a negative effect, regular exercise, in general, helps your sleep. Simply, that’s because it makes you tired and more relaxed.
Change up your bedtime routine. The bright lights of devices don’t make for a relaxing environment in which to unwind. Instead, turn the lights down low, get warm and cosy, and do something calming. Try reading a book or putting on some gentle music.
Keep a regular sleep pattern. This programmes your body’s internal sleep clock to set this routine. Avoid naps, to enable you to keep your routine.
Key Takeaways
How much deep sleep do I need? Generally, about 2 hours a night in the context of 7 to 9 hours of total sleep. If you’re someone who needs less sleep generally, though, you will probably get less deep sleep.
If you’re looking to boost the time you spend in deep sleep, try to ditch caffeine and alcohol. Regular exercise is something that should improve your sleep too.
¹Doris Moser, Peter Anderer, Georg Gruber, Silvia Parapatics, Erna Loretz, Marion Boeck, Gerhard Kloesch, Esther Heller, Andrea Schmidt, Heidi Danker-Hopfe, Bernd Saletu, Josef Zeitlhofer, Georg Dorffner (2009). Sleep classification according to AASM and Rechtschaffen & Kales: effects on sleep scoring parameters: https://pubmed.ncbi.nlm.nih.gov/19238800/
²University of California – Riverside (2016). How the brain consolidates memory during deep sleep Using a computational model, study explains how hippocampus influences synaptic connections in cortex: https://www.sciencedaily.com/releases/2016/04/160414214830.htm
³Y Takahashi, D M Kipnis, W H Daughaday (1968). Growth hormone secretion during sleep: https://pubmed.ncbi.nlm.nih.gov/5675428/
⁴NHS.uk – Why lack of sleep is bad for your health: https://www.nhs.uk/live-well/sleep-and-tiredness/why-lack-of-sleep-is-bad-for-your-health/
⁵Christopher Drake, Ph.D., F.A.A.S.M., Timothy Roehrs, Ph.D., F.A.A.S.M., John Shambroom, B.S., Thomas Roth, Ph.D. (2013). Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed: https://jcsm.aasm.org/doi/10.5664/jcsm.3170
⁶Christopher E. Kline, Ph.D. (2015). The bidirectional relationship between exercise and sleep: Implications for exercise adherence and sleep improvement: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4341978/
While we've ensured that everything you read on the Health Centre is medically reviewed and approved, information presented here is not intended to be a substitute for professional medical advice, diagnosis, or treatment. It should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.
