What is REM sleep? Sleep stages explained in plain English

You may have seen a sleep chart split into blocks of deep, light and REM. But what do those stages mean, and should you worry if one looks short?

Here is how a night of sleep works, what REM sleep is, how it differs from deep sleep, and how the Thrive Health Band and the Thrive by Optihealth app show your own sleep stages.

How a night of sleep works

Sleep isn't one long, even state. Through the night you move through cycles, each lasting roughly 90 minutes, and an adult usually has four to six cycles on a full night.

Each cycle passes through:

Light sleep. The first step down from being awake. Breathing and heart rate settle, and you can be woken fairly easily. It makes up a large share of the night.
Deep sleep. The slowest, steadiest stage. It is harder to wake from, and it is linked with feeling physically restored the next day.
REM sleep. Short for rapid eye movement. Your brain becomes much more active, and this is when the most vivid dreams tend to happen.

Brief moments awake between cycles are normal too.

What is REM sleep?

During REM sleep your eyes move quickly behind closed lids, your brain activity looks closer to being awake, and breathing and heart rate become less regular. Most muscles relax so fully that your body stays still, which is thought to stop you acting out dreams.

REM is linked with memory, learning and processing emotions, which is one reason short nights can leave you foggy or short-tempered.

Your first REM period usually starts about 60 to 90 minutes after you fall asleep and is fairly short. As the night goes on, REM periods get longer, so a good share of your REM comes in the last few hours before you wake.

REM sleep vs deep sleep

The two stages are easy to mix up, but they behave quite differently:

Deep sleep comes mostly in the first half of the night. Your body is at its most settled, and it is linked with physical restoration.
REM sleep comes mostly in the second half of the night. Your brain is busy, and it is linked with memory and mood.

That timing matters. If your alarm cuts your night short, you lose more REM than deep sleep.

How much REM sleep do you need?

For adults, REM usually makes up about a fifth to a quarter of the night, which works out at roughly one and a half to two hours across seven to nine hours of sleep. Deep sleep is often a smaller share, and light sleep the largest.

These are broad ranges, not targets. Your stages shift from night to night with a late dinner, a drink, hard training, a warm bedroom or a stressful day. One short night of REM isn't a problem; the pattern over weeks tells you far more.

What can affect REM sleep

A few everyday things tend to change how much REM you get:

Short nights. Cutting the end of the night trims the longest REM periods.
Alcohol in the evening. It can make you drowsy but tends to break up sleep and reduce REM, especially in the first half of the night.
Irregular sleep times. Big swings between weeknights and weekends make it harder to settle into steady cycles.
Some medications. Your pharmacist or GP can tell you if a new one might change your sleep.

Simple ways to support your REM sleep

You don't need to chase a perfect number. A few steady habits help your whole night:

Give yourself enough time in bed. Seven to nine hours leaves room for the longer late REM periods. See how much sleep adults need by age.
Keep your wake time steady. A regular wake time, even on weekends, helps your cycles settle.
Have alcohol earlier, or less of it. Give your body a few hours before bed.
Wind down. Lower the lights and keep the bedroom cool. The sleep hygiene basics cover more.
Get morning light. A short walk outside soon after waking helps your body clock. See morning sunlight and your circadian rhythm.

How Thrive shows your sleep stages

Wear the Thrive Health Band to bed and open the Thrive by Optihealth app in the morning. On Sleep detail you'll see how long you slept, a sleep chart of your stages through the night, and a breakdown of deep, light and awake time, plus REM sleep when Precise sleep is turned on. To capture REM, turn on Precise sleep (minute-level) in the app under Settings, Health monitoring. Thrive then measures your sleep every minute, which can use more battery, so you'll need to charge the Band more often than the usual up to 14 days. Week and month views show how your nights compare, and daytime naps appear in their own Nap card. Tap a stage to read a short explanation of what it means alongside a reference range.

The Band has no screen, so it's comfortable to sleep in, and with Precise sleep off, up to 14 days of battery means fewer nights lost to charging. Overnight it also tracks heart rate, HRV and temperature.

Thrive learns what is usual for you right across your health, from sleep, heart and activity to mood, energy, stress, meals, medications and more. So rather than comparing you with a general chart, it can show when your REM or deep sleep is lower than your own normal (REM needs Precise sleep turned on), and what tended to come before it. Your Today's Vitality score includes a Sleep and Recovery driver, and Thrive gives recovery insights including an estimate of how much rest you need to get back to baseline.

In your Daily Check-In you can tag things like alcohol, coffee, work stress or travel, then ask Ask Thrive questions such as:

"Is my REM sleep lower on nights after I have a drink?"
"Do I get more deep sleep on days I train in the morning?"
"How has my sleep changed since I moved my bedtime earlier?"

You can also turn on a bedtime reminder in settings. And if you'd like someone else to see your sleep, Thrive Loops lets you share selected information with a participating trainer, health professional or someone you trust. You decide what to share and with whom, and you can change or revoke access at any time.

When to talk to your GP

If you are waking unrefreshed most days for a few weeks, feel very sleepy during the day, or a partner notices loud snoring or pauses in your breathing, book in with your GP. Thrive isn't a diagnosis, but your sleep trends and history are right there in the app to help that conversation, and Ask Thrive can help you pull together what has changed and when.

Before you buy

You'll need a compatible iPhone or Android phone, because the Thrive app is on the Apple App Store and Google Play, in Australia and eight other countries. The app stores are only for downloading the app, though; they aren't where you buy the Band or a Plan. You can buy at thrivehealthband.com, or at a participating World Gym Australia location or health and wellness clinic.

The Thrive Health Band is A$660 for the first year under the launch offer. That includes the Band, which is yours to keep, and 12 months of the Thrive by Optihealth app, My Health on the web, Health Fingerprint, Ask Thrive, Thrive Loops and your data, paid once upfront. Prices are in AUD and include GST. Free Australia-wide shipping during the launch offer (usually A$14.99).

Nothing renews automatically. After your first year, you can get a new band plus 12 more months for A$660, or keep your band and renew the Thrive Connected Plan for A$240 a year, or A$29 a month with no lock-in.

You're also covered by a 12-month Thrive Care Warranty, and consumer guarantees under Australian Consumer Law always apply. See Returns if something is wrong with your purchase.

Common questions

Is it bad to dream a lot?

Not usually. Vivid dreams are a normal part of REM sleep. If dreams often disturb your sleep, mention it to your GP.

Why does my REM sleep change so much from night to night?

Stages vary with timing, alcohol, stress, training and temperature. Look at the trend over a few weeks, not one night.

Can a band on my wrist show REM sleep?

Yes. With Precise sleep turned on, Thrive shows REM along with deep, light and awake time. Precise sleep measures your sleep every minute, which can use more battery, so you'll need to charge the Band more often. A band on your wrist isn't the same as an overnight sleep study, though. Its strength is showing your patterns over time against your own normal.

For more answers, see Questions.

Sources

Sleep Foundation, REM sleep
Sleep Health Foundation
healthdirect, Sleep

Thrive is intended to support general health, fitness and wellbeing. It is not a medical device and does not diagnose, treat or prevent any condition. If you're concerned about your health, talk to a qualified health professional.