If you’ve ever been roused from a deep sleep, you know just how frustrating (and tiring) it is to wake up before you’re ready. This is because deep sleep is essential for feeling, performing, and thinking at our highest level. Not getting enough sleep isn’t just setting you up for tiredness — it’s forging a future of forgetfulness and chronic fatigue.
If you’re relying on coffee and catnaps to compensate for a lack of deep sleep, a better solution awaits. Here’s what everyone needs to know about sleep stages, physical health, and brain function — plus how to increase deep sleep for a healthier tomorrow.
What Is Deep Sleep? Understanding Sleep Stages
Sleep is comprised of two main states: REM and non-rem sleep (NREM). Controlled by natural variants in brain activity, both of these sleep states are important for helping the body rest and rejuvenate. According to the National Sleep Foundation, NREM sleep is a dreamless, slow-wave state that includes four main stages of sleep.
During the first and lightest stage of sleep, the brain produces alpha and theta waves. This is the stage of sleep often reached during catnaps, and it doesn’t typically leave a person feeling well-rested.
In contrast, stage two is the perfect stage of sleep for an energizing power nap. The second stage of sleep is a light sleep where the brain waves increase to cause spindles on a sleep chart. Then these waves slow down to induce a deeper rest.
Third and Fourth Stages
These are the stages in which the body slows down and dips into a deep, restorative sleep due to an increase in delta brain waves. The third and fourth stages are considered deep sleep, or slow wave sleep (SWS). People in these stages will be harder to wake and will feel more refreshed if they complete the cycle before opening their eyes. Being woken up in this (or any) stage of sleep before it is complete can lead to fatigue, confusion, and lack of rest.
REM (Rapid Eye Movement) Sleep
While adults spend more time in NREM sleep than REM sleep, that doesn’t mean REM sleep isn’t important. About 90 minutes after falling asleep and after the first four stages of NREM sleep, the body dips into REM, the second state of sleep.
REM sleep is marked by an increase in eye movement, heart rate, and blood pressure. Breathing can also become fast, irregular, or shallow (this is the stage where sleep disorders like sleep apnea occur).
REM sleep also speeds up our brain activity and ignites regions of the brain responsible for visual, motor, emotional, and autobiographical processing. It’s normal to experience five or six cycles of REM sleep per night. REM stages tend to lengthen throughout the course of sleep, which is why we often wake up the next day with a vivid dream still clear in our minds. Being woken up mid-REM sleep will likely help you recall a dream, but it’ll leave you feeling tired and sluggish because the cycle wasn’t completed.
Why Deep Sleep Matters
The fundamental reason why slow wave sleep is so important is because it allows for restoration. Sleep is when essential bodily processes get to work. During deeper sleep, hormones are released and regulated, tissues are repaired, muscles are grown, and memory is consolidated. This is also when the immune system has time to restore itself, decreasing inflammation and increasing the body’s ability to protect itself.
Sleep is also important for increasing our motor skills and enabling us to learn new activities efficiently. One sleep study on basketball players showed a link between increased restful sleep and improved athletic performance. The athletes also showed a boost in mood and a decrease in sleepiness, during both practices and games following a good night’s sleep.
Sleep deprivation can rob the brain of its opportunity to reorganize and recharge itself. Research shows that high sleep quality is essential for clearing the brain of toxic byproducts and restoring normal functioning.
Mental and Psychological Benefits of Deep Sleep
In addition to helping your body rest physically, quality of sleep also aids in the management of difficult emotions and mental health problems.
“The dream stage of sleep, based on its unique neurochemical composition, provides us with a form of overnight therapy, a soothing balm that removes the sharp edges from the prior day’s emotional experiences,” said Matthew Walker, a psychology and neuroscience professor at the University of California, Berkeley.
Walker and his team conducted a study that showed REM sleep was critical for suppressing our stress response chemicals so that we can use our dreams to process emotional experiences — ones that may otherwise be too painful to confront in daily life.
REM sleep may also play a role in how the brain responds to fear, stress, and trauma. In a Rutgers sleep study, supported by the National Science Foundation, patients who reported higher levels of REM sleep were found to build up resistance to fear in waking life. These findings helped conclude that REM measurements can indicate a person’s resiliency to trauma, as well as their susceptibility to developing posttraumatic stress disorder.
Deep Sleep and Memory Recall
While both REM and NREM sleep are important for the brain, studies show that the third and fourth deep sleep stages of NREM are particularly important for long-term memory recall. According to a Washington University study, older adults who experience less slow-wave sleep have higher levels of a brain protein linked to brain damage, cognitive decline, and Alzheimer’s disease.
“Poor sleep is a hallmark of Alzheimer’s disease. People with the disease tend to wake up tired, and their nights become even less refreshing as memory loss and other symptoms worsen,” say the study’s authors.
REM sleep, which can only be reached after the SWS sleep cycle, has also been shown to play a role in Dementia. In a study on sleep and dementia, researchers showed that people who developed dementia spent 17% of their sleep time in REM. In contrast, people who didn’t develop dementia spent 20% of their time in the rapid eye movement stage. Not getting enough sleep doesn’t just make you forgetful for a day — it can affect your memory for life.
How Much Deep Sleep Do I Need?
It’s clear that proper memory and cognitive functioning require both REM and deep sleep consistently. But how much sleep do you need for a healthy brain and body? The amount of deep sleep a person needs depends on their age and activity level. In general, 7-9 hours of sleep provides ample time to experience the rejuvenating benefits of deep sleep.
How to Increase Deep Sleep
A proper sleep schedule is crucial for achieving better sleep. For example, maintaining healthy control of your circadian rhythms can ensure restorative sleep and wakefulness at appropriate times, says the National Institute for Neurological Disorders and Stroke.
“Your body’s biological clock, which is based on a roughly 24-hour day, controls most circadian rhythms. Circadian rhythms synchronize with environmental cues (light, temperature) about the actual time of day, but they continue even in the absence of cues.”
Your circadian clock is responsible for body temperature, metabolism, and growth hormones, so nurturing these cycles can ensure that you’re healthier both in sleep and in daily life. One way to regulate your circadian rhythms is to keep bright lights out of the bedroom at night. This includes phones, tablets, and other electronics that emit blue light, which the brain often confuses for daylight.
A well-planned sleep environment is essential to support a bedtime ritual. Healthy sleep habits, like sleeping and waking at the same times everyday, also help establish a sleep routine and adjust your circadian rhythm to a healthy schedule. A good sleep ritual also ties into your sleep environment, as you can create a space that supports your mindfulness routine. Reading a book, taking a bath, and avoiding stimulating technologies and lights can help you wind down more quickly.
Using White and Pink Noise for Deep Sleep
The sounds in your environment determine your ability to achieve deep sleep. Whether a noisy street is keeping you awake or you simply feel things are too quiet, white and pink noise can help you fall (and stay) asleep.
“The use of white noise is recommended as a method for masking environmental noises, improving sleep, and maintaining sleep,” say researchers in a study on white noise and sleep.
White noise helps create a more consistent ambient sound that masks activities inside or outside of the room, such as a door slamming or a car alarm beeping. White noise can be created by anything from a fan to a white noise machine — all that matters is that it provides a soothing, ongoing backdrop for restful sleep.
People looking to increase deep sleep may also benefit from exposing themselves to pink noise. Creating a deeper, more resonant tone than white noise, pink noise is a sonic hue that can be heard in steady raindrops, heartbeats, and the rustle of leaves. Pink noise is believed to increase deep sleep patterns and prolong slow-wave sleep.
Get More Deep Sleep for a Better Life
Getting a good night’s sleep is important for keeping the body’s most important regulatory processes in check. From boosting memory recall to improving stress responses, deep sleep plays a role in both current and future well-being. Understanding the different phases of sleep and using a sleep tracker may help you learn more about your personal sleep patterns — and make healthy changes that improve deep sleep for good.