How Much Deep Sleep Do I Need? 55 Minutes?

How Much Deep Sleep Do I Need
How Much Deep Sleep Do I Need

Last Friday, I wrote about brain waves’ impact on sleep health. One question I received after my post was published was, How much deep sleep do I need? 

First, what is deep sleep, and how does it differ from other types of sleep?

Deep sleep is the period of sleep that will contribute the most to helping us feel refreshed when we wake up in the morning!

Not only do our brain waves slow to their lowest levels during this stage, but so do our heartbeat and breathing. Our muscles relax, and we are the most difficult to wake up. Deep sleep is also known as:

  • Slow-Wave Sleep (SWS)
  • Slow-Wave Activity (SWA)
  • Delta Sleep
  • NREM stage 3 and 4 (classic definition)
  • N3 (updated definition)

 

Deep sleep is not to be confused with

  • NREM stage 1
  • NREM state 2
  • REM sleep

Understanding Sleep Cycles

We cycle through a sleeping pattern approximately every 90 minutes on average throughout the night.  The pattern for a healthy young adult looks like this:

  • Stage 1: Light sleep
  • Stage 2: Medium sleep
  • Stage 3-4: Heavy sleep
  • REM: Active brain wave sleep
  • Stage 1: Light sleep
  • Stage 2: Medium sleep
  • Stage 3-4: Heavy sleep
  • REM: Active brain wave sleep

 

This cycle continues throughout the night about 4 to 6 times, depending on how long someone stays asleep.

How much time do I spend in each stage per night? Here are percentages published by the Institute of Medicine (US) Committee on Sleep Medicine and Research and average times I calculated for an 8-hour night of sleep.

  • Wakefulness during sleep: 5 percent, or 24 minutes nightly.
  • Stage 1: 2 to 5 percent, or 17 minutes nightly.
  • Stage 2: 45 to 55 percent, or 4 hours nightly.
  • Stages 3 and 4: 13% to 23%, or about 1 hour and 26 minutes nightly.
  • REM: 20 to 25 percent, or about 1 hour and 48 minutes nightly.

 

Based on those figures, during 8 hours of sleep, I can go through about five sleep cycles. Averaging 17 minutes per sleep cycle gives me about 1 hour and 26 minutes of deep sleep.

That may be how much deep sleep I want.

But what if I only get 7 hours, with the Institute of Medicine’s lowest percentage of deep sleep? Then the answer to the general question, “How much deep sleep do I need?” is:

55 minutes.

How Much Deep Sleep Do I Need Personally?

I’ll walk through one of my typical nightly sleep patterns based on an EEG reading from this study.

The answer to the question "How much deep sleep do I need" lies in our brain-dictated sleep patterns.
The answer to the question “How much deep sleep do I need” lies in our brain-dictated sleep patterns.

8:00 pm: 

Pre-sleep and transition from Alpha to Theta waves:  

About an hour before bedtime, I start feeling tired. As my brain transitions from alpha brain waves (8 to 13 Hz) to theta brain waves (4 to 8 Hz), it begins to slow down.

Everyone in my family notices when I’m in this stage. I hear comments like, “Uh-oh, Dad’s getting tired.” 

9:00 pm:

Laying my head on the pillow and closing my eyes brings a strong sense of grateful relief, “I’m finally in bed! Yippee!” I’m still awake, but fading fast! 

9:15 pm: 

I’ve reached Non-Rapid Eye Movement (NREM) Stage 1, with Theta waves outnumbering Alpha waves.  

My muscles relax, and my heart rate and breathing slow down. I’m entering the lightest stage of sleep.

My family’s voices and laughter gradually fade into the distance. If someone makes a loud noise or turns on a light, I’ll wake up but usually drift off again with no trouble.

Occasionally, not realizing that I’m already in sleep Stage 1, one of the kids jumps on the bed to say “goodnight.” When they touch my arm or hover over my face, I may suddenly jerk awake with a little yelp.

Thankfully, this momentary wakefulness ends quickly. I’m asleep again within a minute or two. 

9:20 pm:

NREM Stage 2:  Even more Theta waves spread throughout the brain. 

Sometimes I toss and turn for 20 or 30 minutes, but more frequently, I’m in Stage 2 within 20 minutes of crawling into bed. The theta waves still dominate, but I have more difficulty waking than when I was lightly aware just a few minutes earlier. 

K-complex and sleep spindles (short rapid bursts of activity) may interrupt the Theta waves. The thought is that these unique brain waves help us remain asleep in non-threatening situations. 

For example, if my kids try to hug or kiss me goodnight during this stage, I’m much more likely to groan and mumble something before rolling over and continuing to sleep. 

10:00 pm 

NREM Stage 3-4. I’m in slow-wave sleep (SWS), with Delta waves finally upon me. I’ve reached my deep sleep stage when I’m dead to the world!

My kids can laugh loudly and even hop on my bed, and I won’t register their sounds or movements. If they hear me say anything, I’m almost certainly talking in my sleep. 

This stage brings “mundane” dreams. But for the vivid, exciting ones, I’ll have to wait for rapid eye movement (REM) sleep.

10:40 pm 

Rapid-eye Movement (REM): Stage 5 sleep. 

During this peculiar stage, my brain waves accelerate back to Stage 1 or even to my pre-sleep patterns. My eyes move rapidly under my eyelids, but my body remains nearly paralyzed.

Another term for Stage 5 is “paradoxical sleep,” because when we’re in it, our minds are active while our bodies are immobile. Intense dreams may occur, and males may experience penile erections.

10:50 pm:

My first REM sleep of the night doesn’t last long before I start cycling back through stages 1, 2, and then back to deep sleep. 

11:10 pm: 

About two hours after falling asleep, I’ve probably gone through a complete cycle and started returning to deep sleep. 

12:00 am: 

Three hours after falling asleep, I should be starting my second round of REM sleep and remain in it longer than the first round – maybe 15 to 20 minutes. Then I start cycling back up to deep sleep. 

1:30 am:

About four-and-a-half hours after going to bed, I finally hit my third nightly round of REM sleep. It usually lasts closer to 30 minutes. 

2:00 am:

After completing REM sleep round 3, I spend a few minutes in stage 1 and longer in Stage 2. Then it’s 30 minutes of Stage 4 deep sleep before returning to REM Stage 5.

Around this time of night, I might wake up to use the bathroom. Hopefully, I won’t have any trouble falling back to sleep!

3:00 am: 

My fourth round of REM sleep will probably be the night’s longest one.

3:45 am:

Our bodies need time to awaken from deep sleep! . How Much Deep Sleep Do I Need
Our bodies need time to awaken from deep sleep!

Time for one more short stint of deep sleep before my body will start preparing to awaken.

4:00 am: 

I’ll spend the next 30 minutes floating between REM and waking up. Knowing my alarm will go off shortly, my body gradually brings me out of a full night’s sleep. 

4:30 am: 

Wake up! I’ve spent refreshing, exciting seven-and-a-half hours lying in my bed, cycling five times through five different stages of sleep. 

Now, to begin another day of eating healthy plant-based food! 

In conclusion: Coming up with an answer to the question, “How much deep sleep do I need?” was enlightening and fun.

However, while 1 hour might suffice for someone my age,  the most critical question about the amount of deep sleep I’m getting is, “Do I feel refreshed?” 

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