How Much Deep Sleep Do You Need For Better Rest And Recovery?

A guide to deep sleep: 

• Deep sleep is a key stage of the sleep cycle, supporting physical recovery, muscle repair and overall restoration.
• Most adults need around 1–2 hours of deep sleep per night, though this can vary based on age and lifestyle.
• Low deep sleep can lead to grogginess, low energy, reduced focus and slower physical recovery.
• Consistent habits like a regular sleep schedule, limiting screen time and daily movement can help support deeper sleep over time.

You've had a full night in bed, but you wake up feeling like you barely slept… and your sleep score doesn’t make for great reading. Sound familiar? That frustrating feeling often comes down to one thing: deep sleep. 

Sleep isn’t just one long rest. Throughout the night, your body moves through different stages, including light sleep, deep sleep and REM (rapid eye movement). Each of these sleep stages supports different processes¹. Some stages focus on physical recovery. Others support memory and emotional processing¹. Together, they make up a full night’s rest. 

This guide covers what deep sleep is, how much you need, and how to increase deep sleep to support your recovery over time.

What is deep sleep? 

Deep sleep, also known as slow-wave sleep, is one of the key stages of the sleep cycle. It sits within non-rapid eye movement (NREM) sleep and is characterised by slower brain activity compared to the lighter stages². Deep sleep tends to happen more in the earlier part of the night, particularly during the first few cycles³.

During this stage, the body settles into a more stable, restorative state. Breathing and heart rate become more regular, brain activity slows, and the conditions needed for physical recovery fall into place². It's the stage that quietly does a lot of the heavy lifting, laying the foundation for how rested you feel come morning.

What happens during deep sleep?

During deep sleep, the body shifts into a more restorative state. Brain activity slows, breathing and heart rate become more regular, and the conditions needed for recovery fall into place⁴.

This is when the physical repair work really gets going. The body increases the release of hormones involved in tissue repair and muscle growth, while processes like protein synthesis and energy replenishment become more active¹. When deep sleep is disrupted or reduced, it may affect how efficiently this restoration happens over time¹.

Deep sleep vs REM sleep: what’s the difference?

Deep sleep and REM sleep are two key stages of the sleep cycle, each supporting different functions in the body. 

Deep sleep is more closely linked to physical restoration. During this stage, the body focuses on processes like tissue repair, muscle recovery and immune support, while brain activity slows and the body settles into its most stable state⁵.

REM sleep, on the other hand, is where most dreaming occurs. The brain becomes more active during this stage, supporting memory processing and emotional regulation⁶.

So, is REM or deep sleep better? Both matter. Research suggests the two stages work together to support cognitive function and long-term health, rather than acting independently⁷. A healthy sleep cycle includes a balance of both, supporting physical recovery and mental processing throughout the night.

How much deep sleep should you get a night?

Most adults should get around one to two hours of deep sleep per night, which works out to roughly 10–20% of total sleep time⁸. 

It doesn't all happen at once. Deep sleep occurs in shorter periods throughout the night, usually lasting between 20 and 40 minutes at a time, with most of it front-loaded into the earlier sleep cycles⁸. 

However, deep sleep needs can change over time, depending on age, lifestyle and overall sleep patterns. Research shows that the proportion of deep sleep tends to decrease with age, with older adults typically spending less time in this stage⁸ ⁹.

What happens if you don’t get enough deep sleep? 

Not getting enough deep sleep can affect how you feel the next day, even when you've spent plenty of time in bed. Here are some common signs to look out for:

• Waking up feeling unrefreshed or groggy⁸. 
• Mental fog that makes it hard to feel fully alert and ready to go⁸. 
• Lack of concentration and mental clarity⁸. 
• Lower energy throughout the day, particularly that afternoon slump⁸. 
• Slower physical recovery. Muscles may feel more fatigued⁸. 

These effects vary from person to person and depend on overall sleep patterns. Occasional disruptions are a normal part of life, but consistently low deep sleep may influence how rested and energised you feel over time.

Why is my deep sleep so low? 

Fluctuations in deep sleep are actually common and can be influenced by a range of everyday factors. It's normal for levels to vary from night to night depending on what's happening in your day and evening routine. So what causes a lack of deep sleep?

• Stress: Research suggests that psychosocial stress before sleep may affect how quickly you fall asleep and can reduce slow-wave activity in the early part of the night, which is when most deep sleep occurs¹⁰.
• Screen exposure: Exposure to light from screens later at night has been linked to changes in sleep patterns, including reduced deep sleep in the first part of the night¹¹.
• Caffeine and alcohol: Caffeine has been associated with longer sleep latency and changes in deep sleep patterns that may affect how restorative sleep feels overall¹²˒¹³.
• Disrupted circadian rhythms: When this rhythm is out of sync, through irregular sleep schedules or changes in light exposure, it can affect how sleep stages are distributed throughout the night¹⁴.
• Environmental influences: Evening light exposure may influence how the body transitions into deeper sleep stages¹⁴, while noise can interrupt the natural progression of sleep cycles¹⁵. Research also suggests that certain temperature conditions may actually support deeper sleep¹⁶.

These factors don't affect everyone the same way, and occasional disruptions are a normal part of life. But paying attention to patterns in your routine can help you identify ways to increase deep sleep over time.

How to get more deep sleep

If you're wondering how to improve deep sleep naturally, it's important to start with consistent, everyday habits. Here are some quick tips to improve your sleep to consider:

• Maintain a regular sleep schedule. Going to bed and waking at similar times each day helps support your body's internal clock, which plays a role in how sleep stages are structured across the night.
• Create a comfortable sleep environment. A quiet, dark and cool space may help reduce disruptions and support the body's natural transition into deeper sleep stages¹⁵˒¹⁶.
• Create a wind-down routine. Relaxation techniques before bed have been shown to support slow-wave sleep, suggesting that giving the body time to unwind may influence how restorative sleep feels¹⁷.
• Move your body during the day. Regular physical activity has been associated with improvements in slow-wave sleep, highlighting the connection between daily movement and overnight recovery¹⁸.
• Limit evening screen time. Light exposure and stimulation in the evening can influence sleep patterns, so winding down your screen use before bed may help improve deep sleep¹⁹.

Supporting better sleep, one night at a time

Deep sleep plays an important role in how rested and refreshed you feel, but it's just one part of the bigger picture. Each stage of the sleep cycle works together across the night, and it's completely normal to see variations from one night to the next.

Rather than fixating on a specific number, looking at your sleep more broadly tends to be more useful. Consistency, routine and overall sleep quality often have a greater impact on how you feel day to day than any single stage on its own.

Small, sustainable habits like keeping a regular sleep schedule, creating a comfortable sleep environment and allowing time to unwind are some of the most practical answers to how to get deep sleep that actually works for you.

Read more on the Swisse Wellness Hub with articles like sleep hygiene and the reasons why sleep is so important.

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