There’s sleep. And then there’s deep sleep.
This article is going to mainly focus on the latter, starting with the most logical place – an introduction to what sleep is and why we all need it.
Why do we need sleep?
We need sleep for a number of reasons. Number one, to help us consolidate our memories, which is a process in which our experiences are mentally transferred from our short-term to our long-term memory. Number two, we need sleep to recharge our brain and our bodies.
Sleep is particularly crucial for growing children, who need it to help power their overall development, e.g. their language, social and motor skills and physical development. It’s one of the reasons why children need more sleep than adults.1
How much sleep do we need?
The amount of sleep differs according to our age. According to guidance published by the NHS, most adults need between 6 to 9 hours of sleep every night.2 Meanwhile, children need anything from between 16.5 hours a day (1 week old baby) to 9 hours a night (16-year-old).3
What is sleep?
It’s when neurotransmitters, the nerve-signalling chemicals in our bodies, stop producing serotonin and norepinephrine, which keeps our brain active and awake. Instead, these neurons switch off. At the same time, a chemical known as adenosine, builds up in our blood, causing drowsiness.4
There are five different stages of sleep:5
- Stage 1: Light sleep – the phase between being awake and falling asleep.
- Stage 2: The onset of sleep – body temperature drops.
- Stages 3 & 4: Deepest and most restorative sleep takes place (more on this below). Note: Stage 4 is known as the ‘healing phase’ because it’s when tissue growth and repair takes place, hormones are released and energy’s restored.6
- REM: Takes place around 90 minutes after falling asleep and again every 90 minutes, getting longer later in the night.
What happens during deep sleep?
The middle stages of sleep, stages 3 (deep sleep) and 4 (deepest sleep), are when we experience deep sleep, which is also known as slow wave sleep or delta sleep.7
When we deep sleep our:
- Heartbeat, breathing and brainwaves slow down
- Muscles relax
In turn, deep sleep can help: our brain process and store away memories, let our minds switch off, regulate our hormones, boost our immune system, keep our blood sugar down and make us feel more energised for the day ahead.8
If you’re truly in a deep sleep, then you won’t wake up to loud noises. A bit like REM, deep sleep happens in regular phases. The first can last between 45 and 90 minutes and for longer as the night goes on.9
How much deep sleep do I need?
It’s estimated healthy adults get around 13 to 23% deep sleep a night, which equates to around 62 to 110 minutes for every eight hours of slumber. As for babies and children, 50% of their sleep is divided between stages 1 to 4.10
How do I know if I’m getting enough sleep?
Your body will tell you if you aren’t getting your quota of sleep by giving off one of more of these signs, as well as many other signs too:
- Brain fog –e. when your brain feels a bit foggy and not 100% focused on what you’re doing, which can lead to you doing absent-minded things, such as putting your phone in the fridge or spraying deodorant on your hair instead of hairspray…
- Trouble staying awake – if you’re nodding off on your train journey to work or struggling to keep your eyes open at your desk
- Gaining weight – leptin is a hormone that’s responsible for telling us we feel full. But when we’re tired, these levels drop and means we can constantly feel hungry
- Feeling irritated – mainly caused by the fact you don’t feel energised or have the concentration to deal with things like you usually would
- Hardly exercising – because you’re too tired to do it and aren’t going at all, or are getting there and are feeling too shattered to do anything11
How to get more deep sleep
Getting more shuteye in general can help increase the amount of deep sleep you get. So too can:12
- Taking a hot bath before bed – heat’s said to potentially promote more slow wave sleep
- Having a bedtime schedule
- Eating a low carbohydrate diet
- Not drinking caffeine before bed (read ‘Drinks to make you sleep’)
- Exercising during the day (not at night)
- Winding down at bedtime – e.g. by reading a book or listening to chilled music; lo-fi music, may be an option
- Removing any bright lights or distractions (devices, TVs etc) from your bedroom
- Being comfy in bed – making sure your mattress, duvet and bedding are nice and cosy
Want to improve your sleep? Read this, ’12 things to help you sleep.’
Last updated: 18 September 2020