Deep Sleep: Stages And Importance

According to the Sleep Foundation, the third stage of the sleep cycle, known as deep sleep, can be crucial for numerous bodily processes, including the regeneration of the brain and body. However, deep sleep is just one of several stages in the sleep cycle. These stages normally repeat multiple times throughout a typical night’s sleep, each playing a unique role in the way the human body functions. Understanding these stages can be key to recognizing the full impact of sleep on our overall health. If you’re experiencing sleep difficulties, consider speaking to your doctor and consulting a therapist to identify and address the source of these challenges.

Are you struggling to get deep sleep?

Talking with an online therapist may help

What are the stages of deep sleep?

Deep sleep is one of several stages that can occur when someone is asleep. These stages make up what is commonly known as the sleep cycle, a pattern that typically repeats several times throughout the night. The Sleep Foundation lists the following sleep cycle stages: 

• Stage 1 (N1): The first stage of sleep usually occurs when someone initially falls asleep. During this stage, a person's body generally begins to relax, and their brain activity starts to change. This change typically involves a transition to slower-frequency brain waves than those seen during wakefulness. Stage 1 sleep phases are often short and light, lasting anywhere from one to seven minutes. Individuals in this stage of sleep can be woken up easily. 
• Stage 2 (N2): From Stage 1, a person will often move rapidly into Stage 2, which normally involves a variety of changes in brain and body activity, such as muscle relaxation, reduced body temperature, slower breathing, and a slower heart rate. Brain activity can also slow, making someone more resistant to being woken up than they would be during Stage 1. Stage 2 phases usually increase in duration during the night, each lasting between 10 and 25 minutes. 
• Stage 3 (N3): The third stage, deep sleep, is a phase that typically involves a more pronounced state of relaxation, with heart and breath rates slowing even further. Brain waves can also slow, which could explain this stage’s other name: slow-wave sleep. Deep sleep can last from 20 to 40 minutes, often occurring more frequently during the first half of the night and becoming gradually shorter as time goes on.
• Stage 4 (REM Sleep): The final stage, rapid eye movement or REM sleep, is often associated with vivid dreaming, though dreams may occur during non-REM sleep as well. In addition to the characteristic rapid movements of the eyes, individuals in this stage can experience a state of arousal that may involve an increased heart rate and irregular breathing. REM sleep can play an important role in multiple processes, such as memory, creativity, and learning. This stage may not occur until after a person has been asleep for 90 minutes. While REM phases tend to have a shorter duration initially, they may become longer as the night goes on.

Each of these stages can play a critical role in the sleep cycle and contribute to overall health. However, Stage 3, or deep sleep, may be particularly important for a variety of reasons. 

Why is deep sleep important? 

Deep sleep may have a variety of benefits and serve a key role in multiple bodily processes, such as those discussed below. 

• Hormone release and glucose regulation: Research suggests that human growth hormone (HGH) levels may increase significantly during deep sleep. In children, HGH tends to be an essential component of growth and increasing height. Once a person reaches adulthood, HGH usually works to maintain the structure of the body. In addition, HGH can increase insulin production, which may regulate blood sugar levels in the body. 
• Muscle growth and tissue repair: The first phase of slow-wave sleep may encourage the release of human growth hormone, which can be important for muscle growth and tissue repair. This bodily process can be particularly crucial for those who engage in regular physical activity, as their muscles and tissues could be damaged during exercise. In addition, protein synthesis may increase during the deep sleep phase, which could have a further positive impact on muscle growth and recovery. 
• Memory: Studies have shown that deep sleep may play an important role in enhancing and protecting declarative memories. Declarative memories are typically split into two separate categories: episodic memory and semantic memory. Episodic memory usually relates to the conscious access of long-term memory, often using contexts like the time an experience took place or any associated emotions. Semantic memory also relates to long-term memories, particularly the recollection of numbers, words, and ideas. These processes can be essential to understanding the world around us and functioning in various settings. 

Deep sleep can also have a variety of other benefits, such as improving immune system function and replenishing stores of energy, while also playing important roles in language, learning, and motor skills. Without deep sleep, individuals could experience a variety of consequences, such as fatigue, difficulty learning new information, difficulty staying alert, and challenges with focus and attention. In order to avoid these consequences, it may be necessary to find coping strategies or treatments to help you get deep sleep. 

Are you struggling to get deep sleep?

Talking with an online therapist may help

How to get deep sleep 

While it may be difficult to increase deep sleep specifically, there can be ways to get more total hours of sleep. This can give your body the opportunity to engage in more sleep cycles, which could increase the opportunities for deep sleep. One method that may help to accomplish this is improving sleep hygiene. To do so, the Sleep Foundation recommends the following.

• Create an optimal sleep environment: A loud, bright, or distracting sleep environment may make it difficult to get deep sleep. To create an area that is more conducive to sleep, it could be helpful to use blackout shades and ear plugs, as well as to remove potential sources of distraction from your bedroom. In addition, electronic devices, particularly those that emit blue light, can reduce sleep duration. By taking these out of your room or avoiding their use near bedtime, you may increase deep sleep duration. It could also be helpful to use a white noise machine or fan to mask any noises that may disrupt your sleep. 
• Avoid specific substances: Certain substances, such as alcohol and caffeine, may decrease sleep quality and duration. Consuming either in large quantities (or before sleep) may make it more difficult to reach deep sleep. To avoid this, it can be helpful to reduce caffeine consumption earlier in the day and stay within the recommended limits for alcohol. In addition, it may be helpful to avoid the use of nicotine and other stimulants, as they can have a similar disruptive effect on your sleep cycle. 
• Reduce stress: High levels of stress may make it harder for a person to fall asleep and stay asleep. Reducing stress could increase sleep quality and deep sleep duration. While there are several ways to reduce stress, one potentially effective method is exercising regularly. Exercise could include cardio activities, such as running, biking, and swimming, or those that build muscle, such as weightlifting. Mindfulness practices, such as yoga and meditation, can also be beneficial in lowering stress levels and promoting relaxation before bedtime.  
• Keep a regular sleep schedule: Keeping a regular sleep schedule can help individuals maintain a healthy circadian rhythm or internal clock. Keeping a consistent sleep schedule typically involves going to sleep and waking up at the same time every day, even on weekends or days off. By doing so, you may be able to increase your total amount of deep sleep. Creating a pre-sleep routine, such as reading a book or taking a bath each night before bed, can further signal to your body that it is time to prepare for sleep. 

Certain forms of therapy may also be beneficial, such as cognitive behavioral therapy. Cognitive behavioral therapy for insomnia (CBT-I) can be particularly effective at addressing sleep difficulties. However, in-person CBT-I and other potentially beneficial therapies might not be available to everyone. 

In some cases, a person may not be comfortable commuting to in-person sessions, particularly if they have been having trouble sleeping. Others may lack insurance coverage or prefer to communicate with a therapist via text, video chat, or phone call. In these situations, online therapy may be a convenient and effective alternative. 

Research suggests that online therapy can be an effective approach for the treatment of insomnia. In a 2023 meta-analysis, researchers reviewed seven studies with a total of 3,597 participants to determine the efficacy of digitally delivered CBT-I for insomnia (dCBT-I). They found that dCBT-I typically effectively reduced insomnia severity in the short term and mitigated insomnia severity in the long term. In addition, researchers found that dCBT-I appeared to have comparable effectiveness to traditional in-person CBT-I.