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Doctor explains difference between REM sleep and deep sleep — plus how to get more of each this World Sleep Day
Sleeping well is vital for energy and good health — but getting the right amount of different stages of sleep can make all the difference. Among the various sleep stages, two of the most well-known are REM sleep and deep sleep.
REM sleep is closely associated with cognition and emotions (not to mention vivid dreams). Meanwhile, deep sleep is crucial for immune function, physical restoration, and general well-being.
We need different amounts of each, and cycling through all of the sleep stages, including light sleep (also known as NREM 1 and NREM 2) is important to wake up feeling your best and promote good health over time.
Ahead, we’re diving into all things REM sleep vs deep sleep for Sleep Awareness Week 2025 — including what happens during each stage, when they occur, how much of each we need. Plus, we'll offer our top tips on how to get more of both.
What is REM sleep?
REM sleep is a stage of sleep defined by rapid eye movement. Per a 2020 review published in the journal Current Biology, REM sleep “is a behavioral state, a brain state, a dream state, and a paradoxical state,” which highlights its status as perhaps the most unique sleep stage.
It’s typically classified as its own category compared to NREM sleep (aka non-REM sleep), the latter of which has three stages that include light sleep and deep sleep.
During REM sleep, your brain is almost as active as when you’re awake, says Raj Dasgupta, MD, FACP, FCCP, FAASM, chief medical advisor for Sleepopolis and a quadruple board certified physician in internal medicine, pulmonary, critical care, and sleep medicine.
What is deep sleep?
Deep sleep is also known as slow-wave sleep, as your brain waves notably slow down to prompt significant rest and relaxation.
“Deep sleep is the most physically restorative stage,” says Dr Dasgupta, underscoring its importance to not only help you wake up feeling refreshed but also support overall health and vitality over time.
“Since it’s such a deep state, waking up from it can leave you feeling groggy,” he adds. Moreover, if you don’t get enough deep sleep, you may feel foggy and fatigued the next day — even if you logged the requisite 7 to 9 hours of sleep per night that most adults need.
REM sleep vs Deep sleep: What do they both do?
Both stages are equally as important for us to wake up feeling rested and restored, ready for another day ahead. However, each take on very different roles to achieve this.
The role of REM sleep
- Processes and consolidates emotional memory
- Regulates mood
- Improves memory and problem-solving capabilities
- Develops the central nervous system (including the brain) during early development
“REM sleep is when most vivid dreaming happens,” says Dr Dasgupta. “Your voluntary muscles stay paralyzed so you don’t act out dreams.”
(Note: You can dream during other stages of sleep, but those dreams may be more fragmented and easier to forget upon waking.)
“REM sleep is key for memory, learning, and emotional processing,” he adds.
The role of deep sleep
- Maintains the brain’s learning efficiency
- Promotes cerebral and physical restoration and recovery
- Supports neuroplasticity, metabolism, and immune system function
- Allows the glymphatic system to remove toxins from the brain and waste products from the central nervous system
Deep sleep — also called the N3 stage of NREM sleep — is arguably the most important sleep stage.
“During deep sleep, your brain waves slow way down, your body repairs itself, and your immune system gets a boost,” Dr Dasgupta shares.
“This is also when growth hormones are released,” he adds. This means deep sleep is essential for physical recovery.
REM sleep vs Deep sleep: When do they occur?
“You cycle through different sleep stages throughout the night, with REM sleep occurring about 90 minutes after you fall asleep,” Dr Dasgupta explains.
“The first REM period is usually short, while subsequent REM stages gradually lengthen as you approach the morning.”
Your first REM stage may be only a few minutes in length while the final REM stage can last up to an hour.
On the other hand, deep sleep happens mostly in the first half of the night, says Dr Dasgupta. Since we need enough deep sleep to feel rested — not to mention facilitate major repair and restoration of the brain and body — it makes sense we 'bank' it as early as possible.
REM sleep vs Deep sleep: How much do we need?
How much REM sleep do we need?
In total, REM typically accounts for around 25% of all sleep, or about 90 to 120 minutes per night. However, this requirement varies on a range of factors.
“Age, genetics, stress levels, and lifestyle all play a role,” Dr Dasgupta shares, each of which will dictate whether you need more or less REM sleep to feel and function your best.
“Poor sleep habits, alcohol, and an inconsistent schedule can throw things off, making it harder to get the right balance of sleep stages,” he adds.
How much deep sleep do we need?
It might sound surprising due to deep sleep’s major influence on restoration, immunity, and brain health, but we actually need less of this sleep stage compared to REM sleep.
“Most adults need about 1 to 2 hours of deep sleep per night,” says Dr Dasgupta, “but this isn’t an exact science.”
Unfortunately, deep sleep decreases with age
Again, the ideal amount of deep sleep for you — as well as how much you’ll typically get — will vary on a host of factors such as your age, health conditions, medications, and lifestyle.
“Unfortunately, deep sleep decreases with age,” he adds, so you naturally might log less of it in older adulthood than you did in your 20s and 30s.
Research backs this up, with studies showing that deep sleep (among other elements of sleep architecture) decreased up until the age of 60, when it appeared to plateau.
How to get more REM sleep
While you can’t exactly train yourself to get more REM sleep, there are a number of lifestyle tips and tricks you can adopt to achieve more high-quality sleep on the whole, and thus increase likelihood of getting more REM sleep.
Keep a regular sleep schedule
“If you want better sleep, consistency is key,” says Dr Dasgupta. As such, sticking to a regular sleep schedule is crucial.
As tempting as it may be to cave into a late-night TV binging session or sleep in when you get the chance, inconsistent sleep and wake times are one of the biggest instigators getting in the way of solid rest each and every night.
Tip: Waking up at the same time each morning — even if you had a poor night’s rest prior — is wise since it’ll encourage sleepiness come bedtime, thus helping you bounce back to your regular sleeping window.
Avoid caffeine and alcohol
Dr Dasgutpa also advises limiting caffeine and alcohol, especially in the evening. However, it’ll be in your best interest scaling back caffeine earlier in the day — with research suggesting at least 6 hours before bedtime to avoid sleep disruptions, though this will also vary based on your sensitivity to caffeine.
The amount will also impact your REM sleep. One study of healthy men published in the Journal of Biological Rhythms in 2021 found that participants who had 150 milligrams of caffeine three times daily over 10 days experienced delays in REM sleep, as well as greater difficulty waking up and feeling sleepy when they did, compared to a group that underwent caffeine withdrawal, and a placebo group.
In addition, alcohol reduces the amount of REM sleep you get — not to mention contributes to nighttime awakenings and lowers your overall sleep quality.
Manage stress and anxiety
Stress and anxiety are likely to get in the way of achieving a good night’s rest and a healthy balance of sleep stages.
There is research to indicate that when experimental stressors were applied in studies, REM sleep, deep sleep and sleep efficiency were reduced.
However, some research shows that major stressors may increase REM sleep but reduce deep sleep. REM rebound, which is when we spend more time in REM sleep, may help mental recovery; however, losing deep sleep in the process will be disadvantageous for your energy levels, physical restoration, and long-term health.
As such, Dr Dasgupta advises managing stress through your preferred relaxation techniques — be it reading, meditating, listening to music, doing gentle yoga, or another method — if worry and rumination lead you to have trouble falling asleep or feel poorly rested upon waking up.
How to get more deep sleep
As is the case with REM sleep, you can’t will yourself to boost the amount of deep sleep you get every night. However, following the tips shared above and below can promote more restorative rest and help you get more deep sleep.
Get enough daylight
“Get morning sunlight to help set your internal body clock,” Dr Dasgupta advises. This is especially beneficial to normalize your circadian rhythm (aka your sleep-wake cycles).
Sunlight indicates that it’s time to wake up and will supress melatonin (aka the sleep hormone) production to give you more energy for you morning and afternoon.
Getting daylight as early in the day as possible will also help ensure that melatonin will release at the right time in the evening so you’re primed for sleepiness and snoozing come bedtime.
Increase exercise during the day
Exercise can improve your sleep. Dr Dasgupta advises staying active during the day, which will also play a role in regulating your circadian rhythm. Research shows that boosting your daytime energy expenditure is an effective way to increase deep sleep.
In case you can’t make it to the gym or a workout class, you can simply increase your step count throughout the day. One 2019 study showed this improved sleep efficiency, reduce stress, and lower daytime sleepiness.
To encourage deep sleep, Dr Dasgupta also advises refraining from intense activity too close to bedtime.
While daytime exercise can increase deep sleep and decrease the time it takes to fall asleep, intense nighttime workouts may have the opposite effect.
Create an ideal environment for sleep
Last but not least, your overall sleep environment will have a major influence on how quickly you fall asleep and how restful your ZZZ’s can be.
Of course, you’ll want to invest in the best mattress for your sleeping position, body size, and personal requirements. Beyond that, there are many other elements worth prioritizing to support deep sleep.
“Creating a cool, dark, and quiet bedroom can help you get deeper, higher-quality sleep,” says Dr Dasgupta.
Worthy purchases to create this ideal kind of sleep environment include blackout shades, breathable bedding, fans, and white noise machines or apps.
