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Old 07-01-2019, 08:09 AM
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How does my smartwatch know how I sleep?


If I wear my smartwatch (Huawei* Watch 2 Sport) to bed, it will show me a report on my sleep. It shows light sleep, deep sleep, and REM sleep over time. How does something I wear on my wrist know this?

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Old 07-01-2019, 08:18 AM
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It doesn't know how much you sleep, but it does know when you're moving around. So if you're lying absolutely still for a period of time it assumes you are asleep. If you're moving, it assumes you are not.

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Old 07-01-2019, 08:22 AM
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Originally Posted by TubaDiva View Post
[...]if you're lying absolutely still for a period of time it assumes you are asleep. If you're moving, it assumes you are not.
But how can it tell the difference between light, deep, REM? I figured you needed an EEG for that.
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Old 07-01-2019, 11:35 AM
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But how can it tell the difference between light, deep, REM? I figured you needed an EEG for that.
The Fitbit tracks sleep stage based on heart rate variability that occurs during each stage -- I'd imagine your smartwatch uses a similar methodology.
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Old 07-01-2019, 12:10 PM
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Originally Posted by TubaDiva View Post
It doesn't know how much you sleep, but it does know when you're moving around. So if you're lying absolutely still for a period of time it assumes you are asleep. If you're moving, it assumes you are not.

Jenny
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My fitbit can tell the difference between sleeping and taking the device off and setting it down overnight. But it isn't using heart rate to distinguish, because I have a cheap, bottom tier fitbit that doesn't have that feature.

My guess is that it's looking for some movement, but not too much.
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Old 07-01-2019, 01:24 PM
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My Fitbit also doesn't do heartrate. I specifically got it to track sleep cycles. It sort of knows when I'm "restless" at night. But it misses a lot. All too often it'll think that I'm asleep most of the day and other stupid stuff.
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Old 07-01-2019, 01:29 PM
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Have you tried comparing it to an actual EEG of your sleeping brainwaves? If you had I think you would have discovered that the answer is "It makes a rough guess."
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Old 07-01-2019, 02:48 PM
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Have you tried comparing it to an actual EEG of your sleeping brainwaves? If you had I think you would have discovered that the answer is "It makes a rough guess."
An EEG is not something you just casually decide to go do. I had one 40 years ago, so no, I haven't compared it.
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Old 07-01-2019, 02:48 PM
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I am not a calm sleeper - I toss and turn quite a lot. My fitbit rarely tracks my sleep properly. It thinks I only sleep an hour a night, or maybe a tiny bit more. I usually sleep 6-7 hours a night.
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Old 07-01-2019, 03:02 PM
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It has a direct connection to Santa Claus, who sees you when you're sleeping.
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Old 07-01-2019, 05:21 PM
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How Sleep Tracking Works for Sleep as Android, an Android sleep tracking app:

Quote:
In deep sleep, your muscle movements are suppressed – the sleep graph gets nearly flat.
During light sleep, you tend to toss and turn which manifests as significant peaks in the sleep graph.

Your body movements are directly related to your current sleep phase. In general, the more movement the lighter the sleep.

Last edited by scr4; 07-01-2019 at 05:22 PM.
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Old 07-01-2019, 05:28 PM
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It has a direct connection to Santa Claus, who sees you when you're sleeping.
Okay, that made me smile.
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Old 07-01-2019, 05:35 PM
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How does my smartwatch know how I sleep?


NM

Last edited by Omar Little; 07-01-2019 at 05:38 PM.
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Old 07-01-2019, 05:37 PM
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Well it was manufactured by one of the leading espionage companies, it probably tracks more info about you than just sleep habits.
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Old 07-01-2019, 05:45 PM
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Originally Posted by CookingWithGas View Post
An EEG is not something you just casually decide to go do. I had one 40 years ago, so no, I haven't compared it.
I wasn't expecting you to. It was just a rhetorical device to point out that the smartwatch doesn't actually know how you sleep. It just makes a rough guess based on what it can detect. I.e mainly how much you move your arm, along what axes, and for some watches your HR.
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Old 07-01-2019, 11:49 PM
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I got my Fitbit to monitor my sleep. I have sleep apnea so I thought it would be useful. I have found it not very accurate. It has counted laying in bed reading as being in deep sleep. There have been nights when I got up because I was not sleeping, the fitbit recorded me sleeping all night long.
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Old 07-02-2019, 01:06 PM
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I don't know how this particular watch works. But during REM your body is mostly non-moving, NREM involves more tossing and turning. And typically you cycle between the stages of sleep (e.g. awake-1-2-3-2-1-REM-1-2-3...). Maybe it makes a guess based on the cycling rate?

Quote:
Originally Posted by CookingWithGas View Post
An EEG is not something you just casually decide to go do. I had one 40 years ago, so no, I haven't compared it.
How do you mean? It isn't invasive. I suppose if you're billing for insurance you can't just request it, but if you have access to one it's a trivial procedure.
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Old 07-02-2019, 01:36 PM
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Quote:
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How do you mean? It isn't invasive. I suppose if you're billing for insurance you can't just request it, but if you have access to one it's a trivial procedure.
I mean that you need a doctor's orders to get an EEG, and the way they do the test depends on what the doctor is looking for. I don't know what you mean by "trivial." When I had one, they had me stay up late at night and get up early so I would be good and tired. They needed an EEG while I was asleep. I can't remember how long I was there, but it was more involved than getting a haircut.
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