The Science Of Sleep
Considering it’s something we do every night, we probably don’t give much thought to the act of sleeping – though if you’re an insomniac you may not think about much else, especially when you’re still wide awake at 3am.
We spend about a third of our entire lifetime sleeping. But while we still don’t have all the facts on why we need to sleep, here are some of the things we do know:
- Sleep helps your brain function more effectively while you’re awake.
- It helps your brain process emotions, since parts of the brain that regulate emotion are more active while you’re sleeping.
- Sleep helps your cells to repair and regrow – this is called the restorative theory.
- It saves energy too, as you need fewer calories (studies suggest you need 35 per cent fewer calories when you sleep for eight hours compared with staying awake the whole time).
- Sleep keeps your immune system healthy, with research suggesting sleep deprivation makes you more susceptible to bugs.
- It’s good for your heart too, though scientists don’t really know why – they just know there’s a link between poor sleep and heart problems. In fact sleep is widely thought of as essential for good health overall.
Did you know? Your circadian rhythm – or internal body ‘clock’ – is essential for sleep. This is in tune with nature, lasting 24 hours and influenced by light and dark. When it’s light your body releases hormones that make you feel alert and energetic. When it’s dark, you get a boost of another hormone that makes you feel drowsy (more of this later).
Four sleep stages
While you’re asleep, you go through a series of repeating cycles lasting one to two hours. Each cycle is divided into four stages – three non-rapid eye movement (non-REM) sleep stages and a rapid eye movement (REM) stage:
- Non-REM sleep 1 is the first few minutes when you go from being awake to entering into light sleep. Everything relaxes and slows down, including your heart rate, eye movements and brain waves.
- Non-REM sleep 2 is when you’re still sleeping lightly but more deeply than in stage 1 – this is the longest of all the sleep stages.
- Non-REM sleep 3 is when you start sleeping deeply (which explains why this stage is often called deep sleep). Your muscles are as relaxed as they can be, and your brain waves reach their lowest activity level.
- REM sleep is usually when you dream. Your eyes move under your eyelids and your breathing, heart rate and blood pressure increase.
As for how much sleep we need, there’s no precise answer, since everyone needs different amounts. The NHS says on average adults need seven to nine hours a night. But don’t just get caught up in the numbers. If you’re always tired during the day, you’re not getting enough.
How you fall asleep
Being awake or asleep is under your brain’s control. Some areas of your brain keep you awake, while others promote sleep – when the ‘awake’ parts are active, they keep the ‘asleep’ parts inactive, and vice versa.
The transition between being awake and asleep can be instant – like flipping a light switch. Several things make this happen. For instance, a chemical called adenosine starts accumulating in your cells when you wake up. By the end of the day it suppresses the parts of your brain that keep you awake. This explains why caffeine stops you sleeping, since caffeine blocks the effects of adenosine.
On a chemical level, research shows magnesium aids this process by activating the parasympathetic nervous system, the system responsible for getting you calm and relaxed
First, magnesium regulates neurotransmitters, which send signals throughout the nervous system and brain.
It also regulates the hormone melatonin, which guides sleep-wake cycles in your body
Once you fall asleep there are many things that can disrupt your rest. These include noise, too much light and drinking coffee or alcohol late at night. Stress and anxiety can cause interrupted sleep too, as can medical problems like restless leg syndrome, chronic pain and having to go to the loo frequently (nocturia).
Did you know? Waking up during the night is as much of a sign of insomnia as finding it hard to get to sleep. And with a third of adults affected by sleep difficulties at least once a week, it’s no wonder sales of sleeping aids are soaring (according to Statista, during 2019 demand in the UK for sleeping aids grew by 8.3 per cent).
Hormones and sleep
You may have heard of serotonin and melatonin, but did you realise that they work together to help regulate your sleep?
Serotonin – a neurotransmitter (or brain chemical) – is often called a ‘feel-good’ hormone as it helps you feel positive, relaxed and energised. Serotonin works with melatonin, a neurotransmitter-like compound that promotes sleep.
Melatonin is produced in your brain’s pineal gland when you’re in a dark environment, while serotonin levels rise when you’re in the light. Having good levels of serotonin can help you get more sleep because it can be converted into melatonin. In other words, to sleep well it’s a good idea to have decent levels of both.
You can boost your serotonin levels by increasing your intake of the amino acid tryptophan. Found in bananas, milk, turkey, cheese, nuts, eggs, shellfish and oats; tryptophan can be converted in the body to a molecule called 5-HTP, which is the precursor used to make serotonin and melatonin.
Did you know? Experts have discovered links between peoples favourite sleeping positions and their personalities. 41% of the British population sleep in the fetal position.
Secrets to better sleep
Many things can disrupt sleep, such as stress, anxiety, indigestion, respiratory issues and late-night parties. However 2 simple steps you can take to improve how well you sleep are to establish a healthy, regular daily routine, and try not look at a screen, or any other light-source, for at least 2 hrs before bedtime.
This is because your daily routine teaches your body when to expect sleep on a daily basis, and light is the other signal that your body uses to work out whether it should be sleeping or not.
At the end of the day however; falling and staying asleep are, like a lot of internal body processes, chemical processes. So you do need to ensure your body has the raw materials it needs to enable that process to work properly. Find out more in our Sleep Nutrition article.