Why slow-wave sleep is vital for your physical and mental health
Clinically reviewed by Dr. Chris Mosunic, PhD, RD, MBA
Are you getting enough deep sleep? Explore what slow-wave sleep is and 7 ways it can benefit your mental and physical health. Plus, how to boost your slow-wave sleep tonight.
Ever have one of those mornings where your alarm goes off, and instead of feeling refreshed, you feel like you never slept at all? It can be incredibly frustrating, especially if you were in your bed for a full eight hours. But not all sleep is created equal.
If you’re not getting enough deep sleep—specifically, slow-wave sleep—then you’re missing out on the kind of rest that actually restores your mind and body. Slow-wave sleep (SWS) is like a behind-the-scenes clean-up crew for your brain. It clears out waste, locks in memories, and helps you wake up feeling like an actual functioning human.
When you don’t get enough of it, you can start to feel foggy and it can really affect your mental health. If you’re tired of being tired, there are simple ways you can improve your deep sleep so that you can wake up feeling refreshed and restored. Here’s what you need to know about slow-wave sleep.
What is slow-wave sleep?
Think of slow-wave sleep (SWS) as your brain’s overnight repair shop. It’s the deepest, most restorative stage of non-REM sleep. If light sleep is like tidying up your room, slow-wave sleep is like a full deep clean, where everything gets scrubbed, sorted, and put back in place.
It’s called “slow-wave” sleep because of the slow, high-amplitude brain waves that occur during this stage. These waves signal that your brain is in full-on recovery mode and is storing memories, repairing tissues, and flushing out toxins that build up throughout the day.
Here is more of a breakdown of what’s happening behind the scenes as you get slow-wave sleep:
Your brain is decluttering: During SWS, your brain typically clears out unnecessary information and strengthens important memories.
Your body is repairing itself: Growth hormones are usually released, which helps to repair muscles, rebuild tissues, and strengthen your immune system. If you worked out that day, this is when your muscles are most likely to recover and grow.
Your nervous system gets a reset: During this, your stress hormones drop, which helps to give your body a chance to relax and recharge. This is why getting enough deep sleep can make you feel calmer and more balanced during the day.
Your brain flushes out toxins: Recent research suggests that SWS helps to clear out harmful waste products from the brain, some of which have been linked to conditions like Alzheimer’s disease.
7 benefits of slow-wave sleep
When you get more slow-wave sleep you typically function at your best during the day. You’re sharper, stronger, and more resilient. Here are some of the biggest perks of getting that slow-wave sleep:
1. Memory consolidation: Slow-wave sleep is when your brain sorts through everything and decides what’s important to keep and what’s good to toss. Research shows that during SWS, your brain tends to transfer short-term memories into long-term storage. This helps make it easier to retain new skills, facts, and experiences.
2. Cell repair and growth: During SWS, your pituitary gland typically releases growth hormones, which are essential for repairing muscles and keeping your body in top shape. This is especially important if you exercise regularly because SWS is when your muscles optimally recover and grow stronger.
3. Stronger immune system: While you sleep, your body produces cytokines, which are proteins that help fight off infections and inflammation. When you don’t get enough deep sleep, your immune system can weaken and make you more susceptible to colds, viruses, and even some chronic illnesses.
4. Emotional regulation: Sleeping through the night helps to reduce stress hormones like cortisol and strengthens your ability to handle challenges. When you get enough deep sleep, you tend to be more patient, less reactive, and better equipped to deal with whatever life throws your way.
5. Brain detoxification: Your brain’s glymphatic system, which is kind of like your brain’s plumbing system, flushes out toxins and waste products that build up throughout the day during SWS. Some of these waste products, like beta-amyloid proteins, are linked to neurodegenerative diseases like Alzheimer’s. So, getting enough slow-wave sleep may help to protect your brain in the long run.
6. Metabolic health: When you don’t get enough deep sleep, your body produces more ghrelin, which is the hormone that makes you hungry, and less leptin (the hormone that tells you you’re full). As a result, this could possible lead to overeating, weight gain, and even an increased risk of metabolic disorders like diabetes.
7. Cardiovascular health: Your blood pressure drops, your heart rate slows, and your entire cardiovascular system gets a break during SWS. This nightly reset can help reduce your risk of heart disease and even stroke.
How to boost slow-wave sleep: 9 tips for deeper rest
Continuously waking up groggy and feeling sluggish during the day can really take a toll on your mood and your overall mental wellbeing. If you’re wanting to kiss your exhaustion goodbye, there are plenty of simple ways that can help you get more deep sleep.
Here are 9 tips to help boost your slow-wave sleep — without you having to overhaul your entire lifestyle.
1. Stick to a consistent sleep schedule
Going to bed and waking up at the same time every day can help regulate your circadian rhythm, which is the internal clock that tells your body when to sleep and when to wake up.
To help your brain have an easier time settling into deep sleep, aim to set a general bedtime and then stick to it. (If your sleep schedule is off, here are seven ways to reset your routine )
2. Keep your bedroom cool and dark
Your body temperature naturally drops during slow-wave sleep, and a cooler room can help support this process.
Aim to keep your bedroom around 65°F (18°C) for optimal deep sleep. You could also block out any excess light with blackout curtains or an eye mask as your brain typically sleeps best in total darkness.
Here are six other tips to help you create the best sleep environment.
3. Move your body during the day
Physical activity—especially aerobic exercise like running, swimming, or cycling—can help increase the amount of deep sleep you get at night. Strength training can also really help you get more SWS as well.
Most days of the week, try to get at least 30 minutes of movement in to help set you up for a good night’s rest. But try to avoid intense workouts too close to bedtime, as they might be too stimulating.
💙 Run to Jeremy Siegel’s Mindful Running Music if you’re looking to be a little more present as you move your body.
4. Limit screen time before bed
Scrolling social media, or watching TV or movies before bed can be overstimulating to the brain, making it harder for you to wind down and eventually fall into a deep sleep. If you can, power down your devices and turn off the television at least an hour before bed.
Try winding down by reading a book, listening to a calming podcast, a Sleep Story, or a short meditation.
💙 Press play on the Pride and Prejudice Sleep Story to help you wind down and drift off to (deep) sleep.
5. Be careful what you consume
What and when you eat can potentially impact your sleep quality. To give yourself the best shot at a good night’s sleep, try to eat dinner at least 2-3 hours before bed so that your body has enough time to digest.
Also, aim to limit your caffeine in the afternoon and evening, and to avoid too much alcohol before bed.
6. Try relaxation techniques before bed
A racing mind can be one of the biggest obstacles to getting deep sleep. If stress or anxiety is keeping you up at night, try some relaxation techniques to help your body wind down.
You could do some deep breathing exercises (here are eight of the best ones for sleep), gentle stretching, or yoga. All of these techniques can help release your physical tension and help you relax.
Also, guided meditation and mindfulness can help to ease some of your stress before bed.
💙 Listen to Restful Sleep with Elisha Goldstein if you’re wanting a guided meditation to help you fall asleep with more ease.
7. Optimize your sleep environment
One of the best ways to help you get good rest is to make your bedroom a sleep sanctuary. To help make your room the comfiest it can be, consider upgrading your mattress and pillows if they’re uncomfortable.
You could also get some white noise machines or earplugs if outside sounds disrupt your sleep. (Here are 10 other relaxing sounds that can help you fall asleep.)
A calming lavender scented candle can also go a long way.
8. Take naps strategically
Naps can be great for recharging, but long or late naps can interfere with your nighttime deep sleep. To give yourself a good chance of getting the best deep sleep, aim to keep your naps during the day under 30 minutes. Also, try to avoid napping too late in the afternoon.
9. Get morning sunlight
Your body’s sleep-wake cycle can be heavily influenced by light exposure. Getting natural sunlight in the morning can help regulate your melatonin levels, which can make it easier for you to fall asleep at night and get deeper sleep.
In the morning, try stepping outside for 10–15 minutes. This can help your future self sleep a little easier at night.
Slow wave sleep FAQs
What happens to the body during slow-wave sleep?
During slow-wave sleep, your body enters full repair mode. Your heart rate and your breathing slow down. Plus, your blood pressure drops and your muscles fully relax. This is also when your body releases growth hormones, which can help repair tissues and support your muscle recovery.
While this is all happening, your brain’s also busy consolidating memories and clearing out waste products that build up throughout the day. It’s almost like a nightly reset button where your body restores itself so you can wake up feeling refreshed.
When does slow-wave sleep occur?
Slow-wave sleep happens in the first half of the night, usually during the first two sleep cycles. Each sleep cycle tends to last around 90 minutes, and SWS typically takes place during the early cycles before REM (rapid eye movement) sleep takes over in the later part of the night.
As your sleep continues, the amount of slow-wave sleep decreases, and your REM sleep becomes more prominent. This is why getting a full night’s rest is so important because if you cut your sleep short, it can mean missing out on this deep and restorative stage.
What medical issues are associated with slow-wave sleep?
Not getting enough slow-wave sleep has been linked to a range of health problems. Because SWS can help to detoxify your brain, insufficient deep sleep has been associated with an increased risk of neurodegenerative diseases like Alzheimer’s.
Additionally, it can affect your metabolic health as poor deep sleep has been linked to weight gain, insulin resistance, and a higher risk of type 2 diabetes. Your cardiovascular health can suffer as well because sleep deprivation is associated with high blood pressure and an increased risk of heart disease.
You might also experience depression and anxiety because you didn’t get enough SWS.
How can I get better deep sleep?
One of the best ways to improve your deep sleep is to improve your sleep hygiene. Here are a few ways to do it:
Keep a consistent sleep schedule: Aim to go to bed and wake up at the same time each day. This can help regulate your body’s internal clock.
Get regular exercise: Movement (especially aerobic or resistance training) has been shown to increase the amount of deep sleep you get, but try to avoid intense workouts too close to bedtime.
Manage your stress: Practices like meditation, deep breathing, and journaling before bed can help to quiet your racing mind.
Avoid caffeine, alcohol, and heavy meals in the evening: Staying away from these activities can help prevent disruptions to your sleep cycle and also promote a higher-quality deep sleep.
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