How Much Deep Sleep Do You Need? Why Sleep Is Important

Multiple stages of sleep occur at night, each important in its own way. Deep sleep is a stage of non-REM sleep that the body requires to rest and rejuvenate. However, deep sleep is only one stage of sleep, and the amount of overall sleep you get directly affects how much deep sleep you actually get. How much deep sleep do you need? Below, explore the sleep stages, how much overall sleep you need to ensure enough deep sleep, and what to do to get the best night’s sleep possible.

Why do the brain and body need sleep?

While a good night's sleep is beneficial, scientists have not developed a clear answer for why people sleep. However, they have developed several theories, including the following.  

Inactivity theory

The inactivity theory is one of the earliest theories about sleep. This theory proposes that being inactive at night once kept organisms out of harm’s way because they were less vulnerable than in the daytime. Inactivity theory suggests that sleep was a behavioral strategy for survival that evolved into what is not sleep. 

Energy conservation theory

The energy conservation theory proposes that sleep's primary function in ancient society was to reduce energy demand when food was not plentiful. Energy metabolism is significantly reduced during sleep, which helps organisms conserve resources. Some scientists think this theory may be related to the inactivity theory.

Restorative theory

The restorative theory relates to the long-held belief that the body and brain need sleep for restoration and repair. Some research has determined that significant bodily processes occur during sleep, including muscle growth, protein synthesis, and tissue repair.

Synaptic homeostasis theory

A newer sleep theory is that the number of synapses in the brain increases rapidly when awake and that the brain could eventually become overloaded. Sleep is an opportunity for the brain to strengthen necessary connections and prune unnecessary ones. 

Brain plasticity theory

Another recent theory, the brain plasticity theory, proposes that sleep is correlated to changes in the organization and structure of the brain. This theory may explain why sleep deprivation has such an impact on people’s ability to learn and complete normal functioning,

Types of sleep

Multiple types of sleep exist, each with its own function in the sleep cycle. Sleep is categorized as non-REM and REM sleep.

Non-REM sleep vs REM sleep

Non-REM sleep, or non-rapid eye movement sleep, has three stages. During these stages, a person initially falls asleep and moves from light sleep into deeper sleep, called slow-wave sleep. This deep sleep plays a key role in rest and rejuvenation in the body. Brain activity, heart rate, and breathing slow down, muscles relax, body temperature drops, and eye movements stop. During non-REM sleep, the body builds bones and muscles, repairs tissues, and strengthens the immune system. 

Dreaming occurs in rapid eye movement (REM) sleep. During this stage, brain activity, blood pressure, heart rate, and breathing rate increase, and the eyes move rapidly while closed. The muscles are temporarily unable to move. REM sleep is believed to play a key role in learning and memory.

What happens if you don’t get enough sleep?

Not getting enough sleep can lead to sleep deprivation. When you don’t get enough sleep, you might have difficulty learning and focusing, and your reaction times might be slower. Insufficient sleep can make controlling your own emotions and interpreting the emotions of others difficult. In addition, it can impact your ability to function at work and school or in social situations. 

Not getting enough sleep also has many physical health effects. People who do not get enough sleep have a higher risk of high blood pressure, coronary heart disease, and stroke. Sleep also impacts the body’s metabolism. A lack of sleep leads to higher levels of hunger hormones, insulin resistance, and an increased intake of fatty, salty, and sweet foods. All of these challenges can contribute to obesity, which may be associated with a range of complications.

How much deep sleep do you need?

Understanding how much deep sleep you need can be difficult without considering how much sleep you get in total. Experts recommend that adults get seven to nine hours of sleep every night.

So, how much deep sleep do you need?

The third sleep stage of non-REM sleep is the deepest of the sleep cycle. Of the total amount of time you’re asleep, about 25% is deep sleep, meaning that you need about an hour and 45 minutes to two hours and 25 minutes of deep sleep every night.

Sleep apnea and other sleep disorders 

Many factors can impact sleep quality, including sleep disorders. Below are conditions that can prevent people from getting enough deep sleep or any sleep at all.

Sleep apnea

In sleep apnea, breathing stops and starts multiple times throughout the night. There are two types: obstructive sleep apnea, in which the airway becomes blocked during sleep, and central sleep apnea, when the brain does not send signals to the body to breathe. People with sleep apnea may experience fatigue during the day because they are frequently woken throughout the night by their interrupted breathing, which results in less deep sleep.

Insomnia

Insomnia is a common sleep disorder that prevents people from getting enough sleep. This condition can affect people in various ways. Some may have trouble falling asleep or staying asleep, while others may wake frequently throughout the night. Insomnia can be a short-lived and minor inconvenience or a significant disruption in someone’s life. 

Other sleep disorders

Other disorders that impact sleep include restless leg syndrome, circadian rhythm sleep disorder, REM sleep behavior disorder, and sleepwalking.

What affects sleep quality, non-REM, and REM sleep?

Because deep sleep is the third stage of sleep, you need to get a certain amount of uninterrupted sleep to allow your body to reach this stage. Any factor that affects sleep quality can lead to insufficient deep sleep, including but not limited to the following:

• Age
• Environment
• Work schedule
• Medication
• Travel
• Screen time
• Food intake
• Caffeine intake
• Physical health conditions
• Mental health

Tips for getting enough deep sleep

There are multiple steps you can take to improve sleep habits and encourage sleep, including the following:

• Stick to a regular sleep routine, going to bed at the same time every night and waking up at the same time every day, even on weekends.
• Establish a relaxing bedtime routine, like taking a warm bath or reading a book before bed, to help your body realize it’s nearly time to fall asleep.
• Keep your bedroom as comfortable as possible. Rooms that support good sleep are typically cool and dark and should be as quiet as possible. Use blackout shades or curtains and a white noise machine if needed.
• Avoid eating in the hours leading up to bedtime.
• Get regular exercise during the day.
• Limit caffeine intake, especially in the afternoon. 
• Avoid alcohol and nicotine altogether, especially in the hours leading up to bedtime.
• Take care of your mental health, as many mental health conditions can impact sleep.

Explore sleep hygiene recommendations in therapy

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Support mental health with therapy

Sleep and mental health can be intricately related. A lack of sleep can lead to mental health challenges, and mental health challenges can impact sleep. Stress, along with conditions like anxiety, depression, and post-traumatic stress disorder (PTSD), can prevent you from getting enough deep sleep. If your mental health is impacting your ability to sleep, working with a therapist can help. Sleep therapy can help you learn about and change any behaviors that affect your ability to fall and stay asleep. You can also learn relaxation techniques and other coping skills to manage the challenges of daily life that may be impacting your sleep. 

If you’re interested in starting therapy, you have various options. Online therapy can be a convenient, flexible choice that allows you to work with a provider from the comfort of your home, so you don’t have to worry about commuting to an office or sitting in a waiting room on days when your lack of sleep is catching up with you. With an online therapy platform like BetterHelp, people can be matched with a provider in as little as 48 hours of signing up. In addition, research has found that online therapy can be effective at treating sleep challenges. One study found that digital cognitive-behavioral therapy for insomnia was “a practical and effective approach for lessening insomnia symptoms.” 

Takeaway

Adults generally need seven to nine hours of sleep every night, about 25% of which is deep sleep. If a lack of sleep is impacting your mental health, or if your mental health is impacting your sleep, working with a therapist can help. Consider contacting a provider online or in your area to get started.