Deep sleep: what is it and how much do you need?

Increasingly, sleep deprivation is a silent burden on modern society. Over 70 million Americans suffer from various sleep disorders or intermittent sleep issues on an annual basis. 

While a casual approach to sleep improvement may simply focus on getting in a certain number of hours each day, such a concept doesn’t embrace the full complexity of humanity’s sleep needs. In fact, while sleep can appear boring on the outside, it is quite a dynamic internal process. And not all kinds of sleep are equal in impact—or, arguably, in importance.

Deep sleep, a crucial component of any sleep cycle, is becoming harder and harder to come by in our sleep-deprived world. It’s time to take a good look at how deep sleep works, why it is necessary, and how we can all get more of it.

What is deep sleep?

Powerful delta brainwaves erupt in our heads. Our bodies release a deluge of hormones and proteins. From cardiovascular to digestive, our body’s systems automatically recalibrate.

This is deep sleep - otherwise known as “NREM” (or non-REM) stages three and four.

It’s the physically-reparative stage of sleep. It allows our bodies to heal worn-down muscles and replenish exhausted energy supplies.

But it does so much more than that. During deep sleep, we process memories, reinforce our immune systems, and wash away harmful toxins from our brains.

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Deep sleep prevents an escalation of this physiological stress that is synonymous with increased blood pressure, heart attack, heart failure, and stroke.

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Matthew Walker, From "Why We Sleep"

Matthew Walker, From "Why We Sleep"

dr. matthew walker

Why do we need deep sleep?

Deep sleep is a time of literal stillness. Our heartbeat slows and our breathing relaxes. Although our muscles are not paralyzed as they are in REM sleep, our bodies are quiet and calm. Even our metabolism slows, conserving energy for the upcoming day.

But this stillness belies a flurry of internal activity.

The pituitary gland pumps out growth hormones, which stimulate cell reproduction and regeneration. We replenish reservoirs of adenosine triphosphate (ATP) - the energy currency of the body - in preparation for another day.

Instead of waking weary and fatigued, deep sleep allows us to rise physically rejuvenated and energetic.

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Deep sleep releases proteins, hormones, and therapies that repair our bodies and restore our energy.  If it were a commercial service, it would be a billion dollar industry. But it is within us naturally and is available for free, every night.

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Param Dedhia, MD

Param Dedhia, MD

sleep Science Advisor

As our heart rate slows, our blood pressure drops. Deep sleep provides an opportunity for homeostatic recalibration. Simply put, it’s good for your heart.

Our digestion follows a similar process. With a break from the inflammatory process of eating, our digestive system can relax, recalibrate, and optimize its function for the next day.

Although we are unconscious, our minds are highly active.

Sharp wave-ripples fire in the hippocampus. Large-amplitude slow oscillations erupt in the cortex. Together, the two brain structures cooperate to convert short-term episodic memory into long-term memory.

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Deep non-REM sleep almost hits the save button on those recently acquired informational pieces so that when you wake up the next morning, you have remembering rather than forgetting.

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Matt Walker,

dr. matthew walker

How much deep sleep do you need?

To keep it simple, an adult typically should get seven to nine hours of sleep each night. As deep sleep is only one of four different steps in the continuous cycle of sleep, and deep sleep stages are variable in length throughout the night, it’s hard to “plan” for a certain amount of time spent in deep sleep particularly.

That said, if a good night’s sleep consists of seven to nine hours of sleep, and deep sleep comprises approximately 13-23% of that time spent sleeping, that means about one hour to 100 minutes of deep sleep has been accomplished during a full night of rest.

Clearly, it might be easy to let those precious few minutes of deep sleep go unachieved if our time spent asleep is cut dramatically short—after all, several minutes of non-deep sleep are essentially required as payment for each single minute of deep sleep.

What if we don’t get enough deep sleep?

Without sufficient deep sleep, our bodies will not recover from the stresses of our waking lives. We will wake feeling fatigued. Our muscles will ache and our joints grind. With our energy supplies depleted, exhaustion will arrive early, wearing us down further.

Unbeknown to us, insufficient deep sleep also wreaks havoc on our cognition. Memories that were crystal clear yesterday will fade into the ether, half-remembered or wholly forgotten.

Without deep sleep cleansing our minds, toxic proteins like amyloids will accumulate, killing the surrounding cells and leading to degenerative illnesses like Alzheimer's.

Deep sleep deprivation need not be long-term to deliver harm, either. Just one night of four hours of sleep will drive a 70% reduction in immune cell activity.

How can we improve our deep sleep?

To increase our deep sleep, we must first create the opportunity for it to exist. That means spending enough time in bed. While the old adage advises eight hours of sleep, the CDC prescribes between seven and nine.

But being unconscious for nine hours is rarely enough. The quality of our sleep is impacted by our environment, personal health, and life choices, and continues to change and evolve.

Modern sleep science uncovered a link between temperature and deep sleep. By reducing our core temperature by one or two degrees in the first half of the night, our bodies more readily slip into deep sleep.

The phenomenon’s cause lies in evolutionary biology. Our bodies adapted for natural caves and basic outside shelters - environments that grow cool and dark overnight. Modern bedrooms couldn’t be more different. While sleep scientists recommend temperatures between 60°F and 66°F, most Americans set their thermostats much higher.

We designed the Bryte Balance™ mattress to address the disparity between biological presets and modern life. It uses chilled air to emulate natural sleeping conditions, lowering the sleeper’s core body temperature and promoting the same deep sleep our ancestors would have enjoyed.

But our environment is only half the equation.

Many common substances have sinister sleep side effects.

Consider sleeping pills. The medicines target a set of receptors in the brain to induce a state of unconsciousness - a poor imitation of sleep. In fact, while sleeping pills induce “sleep,” they stymie progression into deep sleep.

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The quality of sleep that you have when you’re on these drugs is not the same as normal, naturalistic sleep. They’re classified as “sedative hypnotics,” so the drugs actually just sedate you - and sedation is not sleep.

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Matt Walker,
The Cut

dr. matthew walker

Alcohol performs a similar function. It lulls people to sleep, but prevents them from reaching the physically restorative deep sleep stage. With both sleeping pills and alcohol, those who take them often wake feeling groggy, weary, and fatigued - despite having “slept” for eight hours.

Caffeine, too, can hinder deep sleep, although the mechanics are different. The chemical blocks adenosine from entering the brain, staving off sleep. When we do slip into a caffeinated sleep, it is often fitful and disrupted. And if our sleep cycles are broken, we often return to the start, preventing us from reaching later stages like deep sleep.

Specific lifestyle changes for improving deep sleep

For those who wonder how to increase deep sleep, rest assured: there are many simple steps that can be taken in pursuit of this important goal.

- Get regular, consistent exercise. Some people fall into the trap of thinking they can’t be physically active because of a lack of energy due to poor sleep. Good exercise, however, can improve sleep quality, (perhaps counterintuitively) providing an active individual with more energy rather than less. For those who struggle to sleep, it is recommended that exercise close to bedtime be avoided, but reasonable physical activity earlier in the day will only help an aspiring deep sleeper’s cause.

- Cultivate a clear mind for sleep. Many of us who struggle to sleep at night do so because our brains “won’t slow down” or our worries “won’t leave us alone.” Mindfulness practices such as meditation, yoga, journaling, prayer, or creating to-do lists for the next day have proven track records as helpful resources to quiet a noisy mind while pursuing sleep. Smart mattresses and relaxation systems can also help. The Somnify™ multisensory, smart relaxation experience pairs soothing sounds with gentle mattress movements to help you drift off.

- Create a comfortable sleep environment. An obvious solution to poor sleep habits is to improve your sleep habitat, turning it into a desirable, comfortable, restful place that you actually want to sleep in. After all, you spend about a third of your life sleeping. You may as well sleep on a mattress, pillows, and sheets that you enjoy. Make your bedroom peaceful, relaxing, and beautiful, and it’s likely that better quality sleep will follow.
Make sleep a true priority. Strive to keep your appointments with sleep time just like you’d honor an appointment with an important friend or associate. Treat your bedtime and wake time with the priority your health deserves, and don’t make excuses to break those appointments.

- Don’t take long naps during the daytime. We may wrongly assume that long daytime naps will leave us feeling more refreshed or caught up on our sleep deficit, but sadly the opposite can be true. Long naps, especially those exceeding half an hour in length, can radically alter our nighttime sleep rhythms, leaving us more sleep-frustrated than ever.
Keep screens far away from your bedtime. Screens sabotage sleep. Critically, the use of phones, tablets, or television while in bed wreaks havoc on sleep quality and quantity. Commit to resisting the impulse to scroll while you fall asleep. This act alone will massively improve your sleep hygiene. Additionally, even while not in bed, avoid screen devices in the time leading up to bedtime. The light emitted by these screens confuses our brain’s wake/sleep rhythms, making sleep harder to come by when we’ve recently had our eyes glued to a screen.

- Avoid sleep-killing substances. If you need to have a drink close to bedtime, strictly avoid caffeine and alcohol and choose water instead. Nicotine also makes sleep more difficult to come by.

- Pick your sleep battles. Paradoxically, sometimes when we can’t fall asleep, we need to stop trying. Don’t spend your time in bed feeling anxious about how late it is and panicking about how you can’t seem to fall asleep. You may be better served by getting up and doing something simple, like reading a book or doing a mindfulness exercise, until you are once again tired and ready to return to bed. But remember to stay away from screens during these times, or you’ll be worse off.

Get more deep sleep with Bryte

We invite you to experience positive sleep breakthroughs—complete with increased deep sleep—by taking advantage of Bryte’s Restorative Sleep Technology. Pairing the best in sleep comfort with the cutting edge of sleep science, Bryte has developed sleep solutions to help the world experience truly restorative sleep.

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