Why is sleep important? Sleep hygiene and the stages of sleep

Have you ever had a day where coffee just doesn’t cut it? Maybe your focus fades, your energy dips or even small tasks feel overwhelming. Sleep is your body’s chance to reset, yet it’s often the first thing we sacrifice for working overtime, binge-watching a series or late-night scrolling. But those lost hours add up – and they can take a toll.¹ So, why is sleep so important for your brain and body? And what actually happens while you snooze? Let’s break it down...

We know what sleep is on a basic level – you close your eyes and drift off into dreamland. But behind the scenes, there’s a lot more going on. Sleep is a natural state of rest where your brain and body remain active, moving through different stages throughout the night. These stages support different processes, from memory and learning to physical rest and recovery. Rather than staying in one type of sleep all night, you cycle through lighter sleep, deep sleep and rapid eye movement (REM) sleep several times before morning.²

Roughly every 90 minutes through the night, your brain cycles through four different sleep stages: ^2,3

• stage 1 (light sleep): the transition from wakefulness to sleep. Your breathing slows, muscles relax and your brain waves begin to shift

• stage 2 (deeper relaxation): your heart rate and body temperature drop, while brain activity becomes more rhythmic as you settle into deeper sleep

• stage 3 (deep sleep): the most restorative phase, where muscle repair, immune function and cell regeneration occur

• stage 4 (REM sleep): your brain becomes highly active, creating dreams and consolidating memories. Your body enters a temporary state of muscle paralysis to prevent you from acting out your dreams

Sleep is your body’s built-in maintenance system. Without it, everything from your mood to your metabolism takes a hit.³ But what’s actually happening to your mind, body and overall health?

Sleep supports your brain and memory

While you sleep, your brain is anything but switched off. Sleep helps it process information, consolidate memories and support learning.^4,5 Deep sleep plays an important role in memory, while REM sleep is thought to support processes including emotional memory and creative problem-solving.⁵ Emerging research suggests sleep is linked with the brain’s glymphatic system, which helps move and clear waste products like beta-amyloid. Scientists are still researching how this may relate to long-term brain health.^6,7 Research has also found associations between sleep problems and cognitive decline, though scientists are still investigating exactly how sleep may influence long-term brain health.^8,9 For example, sleep problems (including not getting enough sleep, sleeping too much and sleep disturbances) are associated with a faster rate of cognitive decline.^10,11

Sleep helps regulate mood

Sleep plays an important role in emotional regulation and mood. After a poor night’s sleep, you may find it harder to manage stress and emotions.¹² Proper sleep also helps you process emotions, helping you handle the ups and downs of everyday life.¹³ If you’ve ever had a rough night’s sleep, you can probably relate – everyday decisions and problems can feel much more of a bumpy ride.

Sleep supports your immune system

While you sleep, your body releases proteins called cytokines that help fight infections, reduce inflammation and manage stress.¹⁴ Getting enough sleep helps support normal immune function and recovery. According to the NHS, people who sleep for less than six or seven hours each night are more likely to pick up infections – and people with ongoing sleep shortages may even experience a reduction in vaccine effectiveness.¹⁵

Sleep helps control hunger and metabolism

Sleep regulates the hormones that control appetite and metabolism, including:^16-19

• ghrelin (the hunger hormone)

• leptin (the fullness hormone)

• cortisol (the stress hormone)

Overall, not getting enough sleep has been linked to a higher risk of obesity.^20,21 Poor-quality sleep may also affect your body’s response to insulin.²² And there’s the everyday impact: when you’re tired and low on energy, healthy habits can feel that little bit harder. You may be less likely to exercise and more likely to reach for foods higher in fat, sugar or salt.²²

Sleep supports heart health

During very deep sleep, known as stage three sleep, your heart rate slows and your blood pressure drops to give your cardiovascular system time to rest and recover.^2,22 Regularly not getting enough sleep – or having your sleep frequently interrupted – has been linked with a higher risk of high blood pressure.²² Sleep also plays a role in processes linked to heart health, including inflammation and the regulation of stress hormones. Over time, these factors may also influence the risk of heart disease and stroke.^23,24,25

Sleep supports physical performance and recovery

Got gym goals or just want to stay strong as you age? Don’t skimp on sleep, as deep sleep plays an important role in muscle repair and recovery. Growth hormone levels rise at night, supporting muscle growth and tissue regeneration.^26,27 And it’s not just about what happens overnight. Getting enough sleep can help you feel rested and ready to move the next day – whether that’s hitting the gym, heading out for a walk or simply keeping active.

Sleep gives your skin time to recover

They don’t call it beauty sleep for nothing. Quality sleep helps support your skin’s barrier, maintain hydration and keep skin looking healthy and resilient.^28,29,30 Sleep deprivation may disrupt the release of hormones and inflammatory markers involved in skin health, which could potentially worsen existing skin conditions.^31,32

So, you think you can function just fine on a few hours of sleep? Your body begs to differ. Even short-term sleep deprivation can affect your brain, body and emotional wellbeing.³³ Over time, regularly not getting enough good-quality sleep may affect some of the processes we’ve covered above and has been associated with:

• changes in immune function ^14,15,34

• poorer brain function – including attention, decision-making, learning and recalling information ^4,29

• an increased risk of certain neurodegenerative diseases ^8,36

• changes in mood and mental wellbeing ^13,37,38

• increased signs of skin ageing ^29,30

• changes in metabolism and appetite-related hormones ^16-19

The NHS recommends that most adults get between seven and nine hours of quality sleep per night.³⁸ Everyone is different, so this amount can vary slightly. If you’re regularly getting much less than this, struggling to sleep or feeling tired despite getting enough sleep, it’s worth speaking to your GP.

You might have heard the term ‘sleep hygiene’ in your search for better ZZZs. It simply means creating habits that set you up for better sleep – for example, limiting screen time before bed, spending time outdoors during the day, reducing caffeine in the afternoon or creating a comfortable space to sleep in. These healthy habits may make it easier for you to fall asleep faster and reduce sleep disturbances, helping you get better-quality rest.

Sleep might be your first compromise when things get busy, but it deserves a place alongside nutrition and exercise when it comes to looking after your health. After all, prioritising good sleep is one of the best things you can do for both your physical and mental health.³³ By understanding how much sleep you need, recognising the risks of sleep deprivation and making small changes to your routine, you can help boost your mood, improve concentration and enhance your overall wellbeing.^4,12,33 Tonight, why not put your phone down a little earlier, wind down with a calming activity and give sleep the time it deserves?

Fed up with tossing and turning through sleepless nights? Check out 12 simple habits to help you sleep better or shop our top products to help you unwind.

Disclaimer – This article provides informational advice and is not a substitute for medical care. Working with experts for accuracy, we take great care to ensure the information is up-to-date and relevant. However, you should always consult your GP or healthcare professional before using supplements or alternative products, particularly if you have medical conditions or are under supervision.