Different types of sleep explained

You might think that once your head hits the pillow and you drift off, your body simply switches into sleep mode until morning. In reality, there’s quite a lot going on beneath the duvet.

Throughout the night, your brain and body move through different stages of sleep, from those first light moments of dozing to deep, restorative sleep and dream-filled REM sleep.

Each stage has a different job to do, and together they form your sleep cycle. So, what are the different types of sleep, how long do they last and is there one type you should be getting more of? Let’s tuck into the science.

There are two main types of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.

NREM sleep is split into three stages:

• Stage 1 (N1): very light sleep

• Stage 2 (N2): light sleep

• Stage 3 (N3): deep sleep

REM sleep is a separate type of sleep and is the stage most strongly associated with vivid dreaming.

Together, N1, N2, N3 and REM make up the four stages of sleep. Rather than staying in one stage all night, you move through them in repeating cycles.

Think of your sleep cycle as your nightly route through several different neighbourhoods of sleep. You don't simply descend into deep sleep and stay there until your alarm goes off.

A full sleep cycle generally takes around 80–120 minutes, and most people complete roughly four to six cycles during a night's sleep.

The balance changes as the night progresses, too. Deep sleep tends to be concentrated earlier in the night, while REM periods generally become longer towards morning.

That’s one reason getting a full night's sleep matters: cutting your night short doesn't simply remove more of the same sleep. It can affect how much time you have to move through all of its different stages.

You know that lovely floaty feeling when you're not quite awake but wouldn't confidently say you're asleep either? Welcome to stage 1 sleep, or N1.

This is the lightest stage of NREM sleep and your bridge between being awake and properly snoozing. Your body begins to relax, your breathing and heartbeat start slowing and you can still be woken fairly easily.

It doesn't usually last very long. In fact, you may pass through this first stage in only a few minutes.

You might also experience a sudden muscle twitch or the strange sensation that you're falling as you nod off. Nothing like your own leg giving you a surprise just as you're getting comfortable.

Next comes N2, another form of light sleep, although you're more firmly asleep by this point.

Your heart rate and breathing continue to slow, your muscles relax and your body temperature drops. Brain activity also changes, with distinctive short bursts of activity occurring during this stage.

Stage 2 isn't just a brief stop on the journey towards deeper sleep. Adults typically spend a substantial part of the night here, so light sleep is an important part of healthy sleep rather than something you need to avoid.

Stage 3, or N3, is deep sleep. It's also sometimes called slow-wave sleep because of the slow brain-wave activity associated with it.

Your heartbeat and breathing are at some of their slowest levels during this stage and your muscles are deeply relaxed. You're also much harder to wake up — so if you've ever emerged from an alarm feeling as though you've temporarily forgotten which planet you're on, you may have been woken from deeper sleep.

Deep sleep is associated with important restorative processes and physical recovery. Most of it tends to occur during the first half of the night.

If you're prone to grinding your teeth in your sleep, it can happen across different sleep stages, so persistent night-time grinding is worth paying attention to.

REM stands for rapid eye movement, named after the quick movements your eyes make behind your eyelids during this stage.

Your brain becomes much more active during REM sleep, reaching levels of activity that have similarities to being awake. Meanwhile, most of your muscles are temporarily prevented from moving.

And then there are the dreams.

Dreaming isn't exclusive to REM sleep, but this is the stage most closely associated with vivid and memorable dreams. REM is also considered important for processes including memory and emotional regulation.

Your first REM period usually arrives after you've been asleep for a while, and REM periods tend to get longer as the night progresses.

There's no perfect nightly scorecard you need to hit. Sleep stages naturally vary between people and from one night to another, and factors such as age and your recent sleep can change the balance.

For adults, REM sleep commonly accounts for around 20–25% of total sleep, while deep sleep often accounts for around 10–20%. A large portion of the rest is spent in lighter NREM sleep, particularly stage 2.

These figures are better thought of as general patterns than nightly targets. Rather than trying to micromanage every percentage on a sleep tracker, focus on giving yourself enough opportunity for good-quality, uninterrupted sleep.

If you use a smartwatch or sleep-tracking app, you may have come across the term core sleep.

This can be confusing because “core sleep” isn't one of the four standard sleep stages used to describe sleep clinically. Some consumer sleep trackers use the term to group periods of lighter NREM sleep together.

So if your watch tells you that you had several hours of core sleep, don't go searching for a mysterious fifth stage. How “core sleep” is defined can depend on the device you're using.

“Restorative sleep” is another term you'll often hear, but it isn't a separate official sleep stage.

Instead, it's a useful way of describing sleep that leaves your brain and body feeling properly rested and recovered. Deep sleep is strongly associated with physical restoration, while REM sleep plays important roles in brain function, memory and emotional processing.

In short, good-quality sleep isn't about winning a competition for the most deep or REM sleep. Your body needs the whole cycle.

It's tempting to rank the different stages of sleep, especially when your sleep tracker presents them neatly in a graph each morning. But there isn't really a winner.

Deep sleep and REM sleep perform different functions, and both form part of healthy sleep.

Deep sleep is particularly associated with physical recovery and restoration, while REM sleep is linked with functions including memory and emotional processing.

The reassuring news is that you don't need to consciously control your sleep stages. Your body handles the complicated bit while you're snoozing.

What you can do is create the right conditions for consistent, good-quality sleep.

Going to bed and getting up at similar times helps support your natural sleep-wake rhythm. A regular routine can make winding down feel easier too.

Our guide to sleep hygiene has plenty of simple ways to build better habits around bedtime.

Because your sleep stages repeat throughout the night, regularly cutting your sleep short may reduce your opportunity to complete enough full cycles.

Rather than obsessing over individual stages, start by protecting your overall sleep time.

A bedroom that's cool, dark, quiet and comfortable can help create a more restful environment.

And don't overlook the surface you're sleeping on. If you're spending the night tossing, turning and trying to find a comfortable position, it may be worth checking whether your mattress is still giving you the comfort and support you need.

Give your brain a few gentle clues that bedtime is approaching. Dim the lights, put work away and choose something relaxing, whether that's reading, stretching or enjoying a warm bath.

If you need a little inspiration, explore our favourite natural sleep remedies for more ideas.