Far from being a passive state, sleep involves a series of complex interactions inside your body and brain. So what actually happens when you’re asleep?
Written by Madeleine Bailey on March 25, 2019
Reviewed by Dr Neil Stanley on March 28, 2019
A good night’s sleep doesn’t just help you feel okay the next day – it’s essential for your health, too. Here’s why you need it, and how to make the most of your nocturnal slumbers.
What is sleep?
Sleep is a behavioural state that creates a shift of consciousness, and leads to changes in the following:1
- brain-wave activity
- heart rate
- body temperature
We spend a third of our lives asleep,2 so it’s essential to make sure you’re making the most of it. There are two main types of sleep:3
- non-rapid eye movement (non-REM) – this has three stages, from light to deep sleep, in which your brain waves slow down, breathing deepens and restorative processes take place
- rapid eye movement (REM) – this is the dreaming stage. Your breathing and heart rate speed up, blood pressure increases and muscles are temporarily paralysed
What makes us fall sleep?
When darkness falls, the light-sensitive cells in your eyes relay this message to your brain. This prompts the release of the hormone melatonin, which initiates a cascade of events resulting in sleep.4
How much sleep do we need?
On average, we need:5
- babies – 16-18 hours sleep
- children and teenagers – 9.5 hours
- adults – 7-9 hours
A complete sleep cycle, going through all stages of REM, light and deep sleep, usually lasts about 90 minutes.6
What if you don’t get enough sleep?
Sleep has an important restorative effect on all our body tissues and systems, including the immune system, cardiovascular system, muscles and cell repair.7
As well as making you feel tired, poor sleep can: 8
- impact your concentration and memory
- raise your risk of developing anxiety or depression
- lead to weight gain – sleep helps rebalance two appetite hormones, ghrelin and leptin
- reduce your immunity
- affect fertility
- lower libido
- raise your risk of heart disease – a shortage of sleep is linked to inflammation, an increased heart rate and high blood pressure, which can strain the heart
US researchers also think poor sleep interferes with the brain’s routine removal of amyloid proteins, which may increase the risk of developing Alzheimer’s disease.9
What stops us from sleeping well?
Various health conditions can interrupt a good night’s sleep, including:10,11
- anxiety or depression
- sleep apnoea – when breathing is repeatedly interrupted during sleep
- restless legs syndrome – uncomfortable sensations or the urge to keep moving your legs
- menopause – hot flushes can cause sleep problems12
Lifestyle and environmental factors can also interfere with your ability to nod off and stay asleep:13,14
- too much caffeine – this temporarily blocks adenosine, the chemical responsible for sleep drive (the natural urge to fall asleep)
- certain medication
- excess alcohol before bed – this can interfere with sleep quality
- exercising too late – vigorous activity increases levels of the stress hormone cortisol
- staring at screens late at night – the blue light emitted from your phone, tablet or laptop suppresses melatonin production
- interruptions to your circadian rhythms such as shift work or jet lag, which upset your natural sleep-wake cycle
- being too hot or cold
How to get better sleep
Your bedroom should be dark, quiet and cool, at about 16-18°C, according to The Sleep Council.15 Ditch technology from your bedroom, including the TV, smartphones and tablets, as these can tempt you to switch on when you should be dropping off.16
Avoid vigorous exercise before bedtime, but gentle activities like yoga or stretching can actually help you fall asleep.17 You could also have a warm bath, as this helps your body reach the right temperature for sleep.18
Finally, set your alarm to get up at the same time every day. This helps your body and brain get into the routine of preparing to wake roughly 90 minutes before you do actually wake up.
Certain natural remedies may help improve your sleep too:
- 5-HTP – a 2010 US study found a combination of 5-HTP plus an amino acid formula called GABA improved quality of sleep in people with sleep disorders19
- valerian – this herb is approved by the European Medicines Agency for sleep disorders and to aid sleep20
- chamomile – drinking chamomile tea improved sleep quality in new mums, according to a 2016 study in Journal of Advanced Nursing21
If you regularly have difficulty sleeping, and it’s affecting your ability to carry out your daily tasks, it’s important to see your GP. They can offer support and advice to help you get your sleeping back on track.
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
1. Harvard Medical School. The characteristics of sleep
2. National Institute of Neurological disorders and Stroke. Brain basics: Understanding sleep
3. As above
4. As Source 2
5. National Heart, Lung and Blood Institute. Sleep Deprivation and Deficiency
6. Amie M. Gordon. Psychology Today. Your Sleep Cycle Revealed
7. As Source 5
8. NHS. Why lack of sleep is bad for your health
9. Laura Beil. ScienceNews. The brain may clean out Alzheimer’s plaques during sleep
10. The Sleep Council. Sleep Disorders
11. Mayo Clinic. Sleep disorders
12. National Sleep Foundation. Menopause and sleep
13. Harvard Medical School. External Factors that Influence Sleep
14. Alina Bradford. LiveScience. How Blue LEDs Affect Sleep
15. The Sleep Council. Seven Steps to a Better Night’s Sleep
16. As above
17. NHS. How to get to sleep
18. As above
19. Shell W, et al. A randomized, placebo-controlled trial of an amino acid preparation on timing and quality of sleep
20. European Medicines Agency. Valerianae radix
21. Chang SM, Chen CH. Effects of an intervention with drinking chamomile tea on sleep quality and depression in sleep disturbed postnatal women