You may have heard that adults need 7 to 9 hours of sleep each night.

But something that may not be heard very often is that just as important as the duration of sleep is the quality of our sleep .

This is because while you rest, your body goes through different stages of the sleep cycle. Deep sleep, for example, is the stage of sleep you need to feel refreshed when you wake up in the morning.

But what exactly is deep sleep and how can you ensure that you achieve it every night?

In this article, we'll break down the basics of deep sleep and explain ways you can increase deep sleep for optimal health and well-being (spoiler: a gravity blanket can help!).

What is deep sleep?

So, what is deep sleep?

Before we can answer that, let's talk about the stages of sleep.

Sleep is not a linear process, as many might assume, but rather a cyclical one. When we fall asleep, the brain goes through several sleep cycles, each lasting about 90 minutes. During each sleep cycle, the brain alternates between two sleep phases:

1. Non-rapid eye movement (NREM) sleep
2. of rapid eye movement or REM (Rapid Eye Movement) sleep.

NREM sleep is characterized by a lack of eye movement and slow brain wave activity. The NREM sleep phase is divided into three substages:

Stage 1: This is the shortest and lightest stage of sleep, usually lasting 1 to 10 minutes and is the transitional phase from wakefulness to sleep. During this stage, your breathing and heart rate are at normal levels while your body relaxes muscles and prepares for sleep.

Stage 2: The second stage also marks the "official beginning" of sleep. During this stage, body temperature decreases, breathing slows down, and there is further muscle relaxation, especially in the neck area. This phase is also characterized by the presence of spindles, which are believed to play an important role in memory consolidation .

Stage 3: This stage is what people are referring to when they talk about deep sleep. Also known as slow-wave sleep and delta wave sleep, stage 3 is the deepest stage of sleep and is generally associated with slow-frequency, high-amplitude signals called delta waves. There is also so much muscle relaxation in the area that people with breathing disorders, such as obstructive sleep apnea, start to have real problems. Stage 3 sleep is also the most difficult stage to wake up from and is characterized by feeling disoriented.

REM sleep: After the brain has progressed through the stages of NREM sleep, it then enters stage 4, also known as REM sleep (it is also the stage where we dream). During REM sleep, brain activity increases, approaching levels seen when you are awake. At the same time, the body experiences a temporary paralysis of muscles with two exceptions: the eyes and the muscles that control breathing. Even though the eyes are closed, they move rapidly, hence the name of this last stage of sleep.

REM sleep usually begins 90 minutes after sleep onset, and the duration of each REM stage increases throughout the night. For example, the first REM stage may last only a few minutes, while the last REM stage may last an hour.

The importance of deep sleep

The benefits of deep sleep go beyond the fact that you feel truly rested and wake up refreshed. During deep sleep, the hippocampus—the complex area of ​​the brain associated with memory storage and learning—takes the information it has accumulated during the day and sends it to the cerebral cortex (the part of the brain responsible for thinking and understanding). This helps strengthen the connections between neurons, making it easier to retrieve long-term memories.

Improved memory and learning aren't the only functions that deep sleep enhances, however. Stages 3 and 4 of sleep are also responsible for:

• Muscle tissue restoration and development
• Building bones and muscles
• Restoring lost energy
• Promoting cell regeneration
• Strengthening the immune system

Additionally, some research suggests that deep sleep plays a vital role in clearing toxic waste from your brain. In fact, according to a new study published in the journal Nature Communications, researchers suggest that brain activity during deep sleep may help clear away proteins, such as amyloid-beta (Aβ) and Tau, that have been linked to Alzheimer's disease.

How much deep sleep do you need?

Although NREM sleep makes up about 75% to 80% of total sleep time, experts estimate that deep sleep only accounts for about 13% to 23% of total sleep time in the average healthy adult. So, if you normally sleep for 8 hours a night, that means you need somewhere between 62 and 110 minutes of deep sleep each night.

Also, keep in mind that our sleep needs change as we age. It has been observed that as people age, they tend to spend less time in the slow-wave delta sleep phase. One possible explanation for this decline in deep sleep could be that older adults often experience sleep disorders. According to one study , up to 50% of older adults report difficulty falling asleep and staying asleep . Also interestingly, research shows that men experience a more pronounced decline in deep sleep compared to women.

How do you know if you are achieving satisfactory deep sleep at night?

Although sleep monitors are often advertised for their ability to track deep sleep, they are usually extremely inaccurate. In fact, the only real way to know whether you are getting deep sleep at night is through a formal exam at a sleep study center.

During this sleep study, researchers will record your brain's electrical activity as you move from one stage of sleep to another.

Of course, this process isn't the most practical option for everyone. Another thing you could do to gauge how well you're sleeping at night is to use a sleep diary and take stock of how you feel the next day. If you feel mentally sluggish or physically exhausted despite getting eight hours of sleep, chances are you didn't get enough deep sleep the night before.

If you feel like you don't know where to start to improve the quality of your sleep on your own, then we suggest you download the free eBook we have written, perhaps the most comprehensive guide on the Greek internet with the 9 Effective Steps to Immediately Improve the Quality of Your Sleep .

How will you increase deep sleep?

Since the discovery of slow waves in the 1930s, scientists have been trying to figure out how to increase deep sleep. While there are some specific things you can do to spend more time in stage N3, most sleep experts agree that the only and best way to increase the amount of deep sleep is to have good sleep hygiene.

With that in mind, here are some sleep hygiene tips to increase the time you spend in each stage of sleep, including deep sleep:

1. Create a relaxing environment that promotes sleep

Before going to bed, set the thermostat to a cool temperature. According to research , the ideal bedroom temperature should be somewhere between 15 and 19 degrees Celsius. In addition, make sure you have blocked out any potential sources of noise, either by using earplugs or a white noise machine. Finally, don't forget to keep the bedroom as dark as possible, without lights, electronic devices, and open blinds. Use blackout curtains or a sleep mask.

2. Avoid consuming caffeine, alcohol and other substances that prevent sleep

Research has shown that caffeine takes 5 to 6 hours to lose half of its initial effect and 10 to 12 hours to lose ¾ of its effectiveness and be metabolized by our body. In other words, if you drink a coffee at 12:00 noon, then at 00:00 midnight ¼ of the caffeine will still be circulating in your brain.

Caffeine reduces the time of deep NREM sleep during the night by 20%, that is, stages 3 and 4 of NREM, in which the most quality and refreshing sleep takes place.

Similarly, alcohol abuse has been associated with sleep disturbances, including lower slow-wave sleep in the second half of the night.

3. Maintain a consistent bedtime routine

Choose a bedtime each night with a goal of getting seven to eight hours of sleep. It's important to stick to your sleep schedule, even on weekends, as this will help stabilize your circadian rhythm, the "internal body clock" that performs essential functions on a 24-hour cycle.

4. Avoid screens before bed

Electronic devices like your smartphone and tablet emit blue light, a form of visible light that interferes with your body's melatonin production and keeps you awake. To mitigate these effects, download a blue light blocking app on your device and limit its use for at least 30 minutes before bed.

5. Find ways to relieve stress

Studies suggest that stress reduces slow-wave sleep , so anything you can do to reduce stress and anxiety before bed will be beneficial for improving your sleep quality.

When it comes to keeping stressful thoughts under control, many people find that gravity blankets help. These therapeutic blankets apply a steady, gentle pressure to the body—known as Deep Tactile Pressure —to relax the nervous system and calm the mind, while also giving you the feeling of being safe under a warm embrace. Don’t worry, gravity blankets aren’t just for the winter months. Try the premium Gravity Ice for deeper sleep even in the summer.

6. Go to bed only when you feel sleepy.

When you repeatedly go to bed without feeling sleepy, your brain starts to associate your bed not with sleep, but with a state of wakefulness. Therefore, you should only go to bed when you start to feel tired and sleepy. If it's getting close to bedtime and you're still not in the mood, try winding down with a relaxing activity (e.g., reading, meditating, taking a warm bath).

Other ways to increase deep sleep

In addition to good sleep hygiene, below you will find some extra scientifically proven ways to increase deep sleep.

1. Exercise regularly

Exercise is a proven way to improve sleep quality. In fact, recent research shows that exercise can improve the quality of slow-wave sleep by increasing the stability of slow waves in the early stages of sleep.

Are you wondering which exercises are best for deep sleep? According to experts, moderate-intensity aerobic exercise (e.g., cycling and brisk walking) is very effective at improving sleep quality. Additionally, strength training exercises, such as lifting and bodyweight exercises (i.e., push-ups, sit-ups, etc.) can help improve many aspects of your night's rest, including deep sleep.

2. Consider hypnosis

Because of the way hypnosis is often portrayed in our pop culture, many people are quick to write off this psychological therapy process as a potential sleep solution. However, hypnotic suggestion has actually shown promising results for improving sleep. In a study from the University of Zurich, researchers found that slow-wave sleep improved by up to 80% in female participants who were receptive to hypnotherapy.

3. Listen to music

When you were a baby, your parents probably sang you lullabies to help you fall asleep. But did you know that relaxing music can help you achieve better sleep quality as an adult? In fact, research shows that listening to binaural beats can help you relax and achieve deeper sleep.

Binaural beats - as they are called in English - are auditory illusions created by the brain when you listen to two different sound frequencies at the same time. When you listen to binaural beats, neurons start sending messages to the brain at the same rate, and according to some experts, this can increase the strength of certain brain waves and help you achieve a specific mental state that is more conducive to deep sleep.

4. Learn something new

Learning new things can improve a range of cognitive functions, including concentration, problem-solving, and attention to detail. And according to some researchers, spending the entire day learning something new can help you enjoy deeper, more restful sleep.

In a 2002 study , German researchers found that participants who spent their day studying and learning had a higher density of sleep spindles compared to those who spent their day doing non-learning activities. While spindles may not increase the amount of time spent in deep sleep, some research suggests that they can help you stay in stages 3 and 4 of deep sleep even when faced with distractions like loud noises.

5. Try aromatherapy before bed

Aromatherapy is another valuable sleep tool that shouldn't be overlooked. The soothing scent of certain essential oils has been scientifically proven to positively affect sleep.

Lavender is perhaps one of the most well-studied essential oils for sleep, and for good reason. Numerous studies show that lavender can induce a state of relaxation, helping the user fall asleep and stay asleep. A recent study also found that the scent of lavender can enhance slow-wave sleep .

Tackle stress and insomnia with a gravity blanket

Gravity blankets are the most effective way to deal with insomnia and stress without medication, as they have been used for many decades to help people suffering from anxiety disorders, autism, and other sensory disorders.

How do they work?

They are designed to apply gentle, steady pressure to the entire body, which occupational therapists call “ Deep Tactile Pressure .” This steady pressure relaxes the nervous system and helps the body naturally increase levels of serotonin and melatonin (the hormones of happiness and sleep) while reducing levels of cortisol, which is responsible for stress.

As a result, the mind stops "racing", the heart rate drops, the mood improves and the body enters a state of complete relaxation.

Choose the one that weighs closest to 10% of your body weight and upgrade your sleep from the very first night.