What Is REM Sleep? Dreams, Muscle Paralysis and Why It Matters

REM sleep is the stage of sleep when your eyes dart about under your lids, your brain becomes busy and most of your vivid dreams happen. It makes up roughly a fifth of an adult's night, and most of it arrives in the last few hours before you wake. This guide covers what REM sleep is, how it fits into your sleep cycles, what it seems to do, what cuts it short, and how your wake-up routine affects it.

The short answer: REM stands for rapid eye movement. It's one of the two main types of sleep, and adults spend about 20% of the night in it. During REM your brain is very active and most of your muscles are switched off, which stops you acting out your dreams. REM comes in every 90-minute cycle but gets longer towards morning, so cutting your sleep short mostly cuts your REM. The best way to get enough is simply enough sleep at regular times.

What REM sleep is

Sleep isn't one even state. Healthdirect describes two main phases: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. In NREM you're in a deeper, quieter state, your body temperature drops, your muscles relax and your heart rate slows. In REM, "your eyes move rapidly" and your mind is very active. This is when the most vivid dreaming happens. Adults spend about 80% of sleep in NREM and about 20% in REM (source).

The Sleep Health Foundation calls REM "dreaming sleep" and notes, in its factsheet on nightmares, that it may play a part in how you remember and process information from the day.

What happens in your body during REM

REM is an odd mix of a wide-awake brain in a mostly still body.

• Fast, jerky eye movements. These give the stage its name, and people woken from REM usually remember dreaming.
• Most muscles are switched off. This is called muscle atonia. Your eyes still move and your breathing muscles keep working, but your arms and legs don't follow your dreams. A review in the Journal of Clinical Medicine explains this matters "so as not to harm oneself or others while sleeping", because the brain keeps sending movement signals that match the dream (source).
• A busy brain. Healthdirect describes your mind as very active during REM, which fits with how lively REM dreams feel.

Sometimes the switch-off and waking overlap. You become aware but your body is still in REM mode for a few seconds or minutes. That is sleep paralysis, which the same review describes as a "mixed" state between REM sleep and wakefulness. It's frightening but usually harmless; more on it in our upcoming guide to sleep paralysis.

How REM fits into the night

Sleep runs in cycles of about 90 minutes. The Sleep Health Foundation notes that the first three hours hold the deepest sleep, and that later in the night "we have more of the sleep stage with vivid dreams". There is REM in every cycle, even if only briefly (source).

Part of the night	What dominates	What it means for you
First 3 hours	Deep (slow-wave) sleep	Hardest to wake from; groggiest if woken
Middle of the night	Mix of light, deep and REM	Brief arousals you mostly forget
Last 2 to 3 hours	Longer REM periods	Vivid dreams; most REM happens here
Just before waking	REM and light sleep	Why you often wake mid-dream

For a fuller walk through each stage, see sleep cycles explained. Deep sleep has its own guide: how to get more deep sleep.

What REM sleep seems to do

Scientists are still working out exactly why we have REM. The main ideas with support are:

• Memory and learning. Healthdirect says REM is vital for learning and creating new memories.
• Emotional processing. Researchers link REM with emotional regulation and mental health.
• A marker of good sleep. A 2021 review in the International Journal of Environmental Research and Public Health found that self-reported sleep quality is positively linked to how much REM people get (source).

None of this means you need to chase a REM number on a tracker. Consumer devices usually estimate stages from movement and heart rate, and the figures can be rough. See do sleep trackers work before you worry about a low score.

What cuts REM short

Because REM piles up near morning, the biggest threat is simply short sleep.

1. Cutting the night short. The same 2021 review notes that sleep restriction significantly reduces REM, and that REM increases again when people are allowed to sleep longer. Getting up an hour early takes a bigger bite out of REM than out of deep sleep.
2. Evening light. The review notes that artificial light in the evening and early night can delay and disturb your body clock, especially affecting REM.
3. Alcohol. The Sleep Health Foundation says alcohol interferes with how you cycle through the normal stages, with more awakenings, night sweats and nightmares in the second half of the night (source). See does alcohol help you sleep.
4. An irregular schedule. REM is tied to your body clock. Constantly shifting bed and wake times, as with social jet lag, works against it.

If you've been short on sleep, your body tends to make up some REM when you get the chance. Many people notice more vivid dreams on a sleep-in, which fits with that rebound.

Waking up in REM

Since the last stretch of the night is REM-heavy, your alarm often lands mid-dream. Deep sleep is the stage healthdirect describes as hardest to wake from, so landing in REM is not the worst case, but a harsh, loud alarm can still make it a jolt. A steady wake time does more for REM than any gadget: it lets your body clock time the final cycles around when you get up. A gentler alarm, such as a vibration that builds, can make the moment of waking less abrupt.

When to see your GP

See your GP if you or your partner notice you acting out dreams (shouting, punching or kicking in your sleep), if nightmares are frequent and distressing, or if you're very sleepy during the day despite enough time in bed. This guide is general information, not medical advice.

Where the Sovune Nudge fits

We make the Sovune Nudge, a vibrating alarm wristband, so we're not neutral. It won't change your sleep stages, but it can make the REM-heavy end of the night finish more gently.

• Wakes you with vibration on your wrist, starting as a gentle tap and building through three intensity levels.
• Silent. No speaker and no sound, so a partner can finish their own last cycle.
• Vibrates for a full minute, stepping up gradually, and you can switch it off sooner.
• Set on the band itself. No app, no phone, no Bluetooth, so no screen in bed.

It comes with a 30-day money-back guarantee.

Quick answers

How much REM sleep do adults need? There's no fixed target, but adults typically spend about 20% of the night in REM. Getting 7 to 9 hours is the simplest way to get enough.

Is REM or deep sleep more important? Both matter and do different jobs. Deep sleep dominates early in the night and REM dominates later, so you need a full night for both.

Why do I remember dreams some mornings and not others? You're more likely to remember a dream if you wake during or just after REM. Most brief night-time wakings are forgotten.

Can I increase REM sleep? Mainly by sleeping long enough, keeping a regular wake time, dimming evening light and going easy on alcohol.

For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.

See the Sovune Nudge →