I started self-measuring with the Jawbone Up 10 days ago. The amount of deep sleep I was getting immediately caught my eye. Here’s the data from one of the first nights:
Straight away I noticed that deep sleep was just 30% of my overall sleep.
It seemed too little to me and while this was my worst night, my deep sleep never climbed above 38%.
So I started wondering: How much deep sleep should I get? What exactly is it? What does it do for me?
Searching for answers
Finding the answers was surprisingly difficult. The major obstacle was to understand how the Jawbone UP defines deep sleep in the first place.
Here’s the problem:
The Jawbone Up (like Sleep Cycle and similar apps) measures our movements and divides them into two phases:
- Light sleep: when you move more
- Deep sleep: when you move less
But this is different from the scientific definition with four (sometimes five) phases.
Let’s see how they compare:
You slowly settle in to sleep.
- Your muscles relax.
- You have light dreams.
- Typical ratio of overall sleep: 5%
And the Jawbone UP?
You move quite a bit: it registers this as light sleep.
The second phase of light sleep.
- Your breathing and heart rate slow down.
- Your body temperature drops a little but your body remains relatively active.
- Typical ratio of overall sleep: a whopping 50%.
And the Jawbone Up?
You still move markedly during this phase: the Jawbone registers these movements as light sleep.
This is the ‘official’ deep sleep-phase.
- Your heart and breathing slow further.
- Your muscles relax and your body hardly moves.
- Your brain is much less active now: you don’t dream.
And the Jawbone UP?
We hardly move during this phase so the Jawbone UP measures it for what it is: deep sleep.
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What happens during deep sleep?
During deep sleep, all energy goes into recharging your batteries: Your kidneys clean your blood, your organs detoxicate, cells are replaced, wounds heal, muscle tissue builds up. Moreover, you consolidate your memories.
Get too little deep sleep and your immune system weakens. Over the long run you may suffer fatigue, apathy and even depression.
Sounds like I want to get enough of that. But how much should it be?
Here’s a surprise: a healthy dose of deep sleep is about 20% of overall sleep. That’s less than I thought.
If this is the case, then even my worst night with 30% would be way above the norm. If we only had three phases, I needn’t worry. But there’s a fourth phase and this is where things get interesting:
Phase 4 (REM sleep):
In REM-sleep the brain gets active again. It’s as active as during the day: we dream intensively during this phase.
It’s not exactly known what REM-sleep does for us but it seems to play a key role in storing memories and balancing our moods – nothing I’d want to tinker with. And 25% of overall sleep is the healthy norm.
But where does it count? Does the Jawbone Up register REM as deep or light sleep?
REM is a paradoxical phase. The name stands for Rapid Eye Movement: our brain is active and our eyes are too. But our limbs are not. We secrete hormones that effectively put us in a narcotic state: like in deep sleep, our body lies still!
And this can only mean one thing:
The Jawbone UP registers REM-sleep as deep sleep. It cannot keep the two apart: it doesn’t look into your eyes and it doesn’t measure your brain activity (you’d need an EEG for that).
So there we go: deep sleep on the Jawbone is both REM- and the real deep sleep.
Let’s look at the ideal ratios again:
- Deep Sleep 20% + REM sleep 25% = 45%.
It’s a bit of a shocker. With 30% in the worst and 38% in the best night, I’m quite a way off. But I have my target now: I want to up my deep sleep to 45% in the next 10 days.
Will I manage? I’ll report about it here.
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