Deep Sleep: Benefits, How Much You Need, How to Get More

Deep sleep is the foundation of physical recovery. Understanding what it is, why it matters, and how to optimize it can help you perform better today and build resilience for the long term.

What is deep sleep?

Deep sleep is one of the 4 stages of sleep (along with light, REM, and wake) that your body spends time in each night. Known as the "physically restorative" stage of sleep, it is of great importance for athletes and anyone focused on recovery and long-term health.

Shortly after falling asleep, your body transitions from light sleep to deep sleep. This is the stage of sleep when your brain waves are the slowest (and their activity is synchronized when monitored with an EEG). For this reason, deep sleep is also referred to as slow wave sleep (SWS).

During this time your muscles relax, and your heart rate and respiratory rate decrease significantly. It can also be difficult to wake up, even when there are loud noises. When you are woken up during this stage, you tend to feel groggy and disoriented.

Your first period of deep sleep each night generally lasts between 45 and 90 minutes. As the night progresses, periods of deep sleep become shorter in the cycles that follow (the average adult typically goes through 3-5 full sleep cycles per night).

Deep sleep and the sleep cycle

Deep sleep and REM (rapid eye movement) sleep are not the same thing. REM sleep follows deep sleep in standard sleep cycles and is the "mentally restorative" stage of sleep — when short-term memories from that day are converted to long-term memories. Unlike deep sleep, the brain is very active during the REM stage, when most dreams occur.

The benefits of deep sleep

Deep sleep is the time during which your body restores itself physically. In fact, 95% of human growth hormone is produced during deep sleep. Working out breaks your muscles down, then deep sleep helps build them back up.

In order to see the greatest potential gains from training, getting a sufficient amount of deep sleep afterwards is essential. The following things also happen during deep sleep:

• The immune system is strengthened
• Cells regenerate, and tissues and bone are repaired
• Blood flow to muscles increases
• Metabolism and blood sugar levels are balanced
• The brain is detoxified

How much deep sleep should you get?

For most adults, deep sleep normally consists of 15-25% of their total time asleep, usually between an hour or two each night. However, deep sleep also decreases with age. Seniors get less of it than adults, and adults get less than children, primarily because growth and development are key aspects of it.

A healthy breakdown to aim for in terms of percentage of time spent in each stage of sleep:

• 50% Light
• 22% REM
• 23% SWS (Deep)
• 5% Awake

What happens when you don't get enough deep sleep?

When you're sleep deprived, deep sleep becomes your body's priority. If you fail to get the proper amount of deep sleep one night, your body will do everything it can to make up for it the next night. For example, even if you have back-to-back nights with below average hours of sleep, on the second night you'll get a disproportionately high amount of deep sleep to compensate.

A consistent, long-term loss of deep sleep is likely an indicator of chronic sleep deprivation. This has been linked to greater risk of obesity, Type 2 Diabetes, heart disease, cancer, dementia, and depression.

How to get more deep sleep

In general, anything you can do to promote better sleep behavior will also help you get more deep sleep — starting by simply spending more time in bed.

One of the most effective methods is maintaining sleep consistency by going to bed and waking up at similar times each day. Your body runs more efficiently when it's on a predictable schedule, and this is particularly true with sleep. An analysis of sleep data from 25,000 WHOOP members showed a distinct rise in amount of nightly deep sleep (SWS) as the percentage of sleep consistency in a 4-day period increased. For WHOOP members, better sleep consistency correlates with more deep sleep.

The other is to avoid drinking alcohol before bed. When your body is busy processing alcohol it has trouble getting past light sleep and into deep sleep. This is especially problematic because a large portion of your deep sleep usually occurs in the first sleep cycle, which is the one most disrupted by alcohol consumed prior to falling asleep.

Monitor your deep sleep with WHOOP

WHOOP measures your sleep in detail each night, telling you exactly how much time you spend in each stage of sleep. You also see the trends over time in your restorative sleep for a closer look at how much you're getting and when for insights into what may impact it.

The WHOOP Sleep Planner uses your natural circadian rhythm to make recommendations for bed and wake times each day. WHOOP will let you know how much deep sleep you're getting and help you better understand what you can do to get more of it.

Understand and improve your sleep with WHOOP

Deep sleep is a cornerstone of your daily recovery and long-term health. By understanding what it is, why it matters, and how your behaviors affect it, you can move from simply viewing your sleep data to actively improving it. The insights from WHOOP provide the data and coaching you need to build habits that increase restorative sleep, helping you perform at your best today and live healthier for longer.

Ready to take control of your sleep? Join WHOOP.

Frequently asked questions about deep sleep

Does deep sleep mean you had good sleep?

While every stage of sleep is important for a full recovery, deep sleep is especially critical for physical restoration. Getting a sufficient amount of deep sleep is a strong indicator of a restorative night, but all stages — light, deep, and REM — work together to support your overall health.

Is it better to have more deep sleep or REM sleep?

Both are vital. Deep sleep focuses on physical restoration — repairing muscles and tissues — while REM sleep is for mental restoration, like memory consolidation. A healthy night's sleep includes several cycles of both, and your body naturally regulates the amount of each stage you get based on your needs.

What does it mean if you get a lot of deep sleep?

Getting a high amount of deep sleep usually means your body is prioritizing physical recovery. This can happen after a period of sleep deprivation, an intense workout, or if you are fighting off an illness. It's your body's natural way of catching up on restoration.

Why does deep sleep decrease with age?

It is common for the amount of deep sleep to decline as you get older. This is partly due to changes in brain structure and sleep architecture over time. While you may get less deep sleep than when you were younger, focusing on consistent sleep habits can help you maximize the quality of the restorative sleep you do get.