Sleep 5.1 How Consumer Wearables Measure Sleep Quality

We cover the physiological measures used by consumer wearables like Apple Watch, Garmin, Fitbit, and Oura ring to assess sleep quality and stages.

Video Breakdown:

00:00 Introduction to Autonomic Nervous System and Sleep

01:10 Consumer Wearables and Sleep Staging

02:44 Physiological Measures in Wearables

03:40 Sleep Scores and Their Components

05:46 Conclusion and Personal Insights

So today's objectives, are several. First, I wanna have the, opportunity to ask and answer this question. So, what physiological measures are used by consumer wearables to assess sleep quality and staging? How does heart rate heart rate variability, movement, respiration and temperature fluctuate across sleep stages? What portable devices can capture these physiological measures and what limitations exist for each? And what is the significance of sleep arousals, and which physiological measures or device can capture arousal and events? And I hope by the end of this talk you'll be able to answer these questions.
And this is how I broke down this talk, into five sections. I will briefly talk about the consumer devices, heart rate, heart rate variability and movement, respiration and temperature. Have a section so dedicated to integrating the information and sleep arousals as well.
So, for the consumer wearables, I decided to focus on these four consumer wearables since they represent a lion's share of the wearable market. Apple Watch , Garmin, Fitbit and Oura. I was interested in to see like how these, consumer wearables broke down sleep. And interestingly, they all break down into four stages.
First with Apple, you see the breakdown into Wake, REM and what they call Core, and Deep. And the reason they call it Core was because, Core is, is a combination of N one, non-REM stage one and non-REM stage two and they felt that Light sort of emphasized a little bit more on the non-REM one as opposed to non-REM two where most of sleep, occurs in non-REM two.
So I think they established the Core instead of Light. Whereas the other three, Garmin, Fitbit, and Oura basically divided, into the Wake, REM, Light and Deep. What I can see from the literature that's out there, Light entails both non-REM one and non-REM two stages of sleep. What is interesting is that they all seem to, represent the data the same way.
You could kind of see it here, basically the Wake is on the top, REM on the next level, Light and Deep. That's done with Garmin, Fitbit, and Oura. I'm not sure why they sort of all agreed to do this, but that's, basically the way it's arranged.
And the question is, what physiological measures in is employed to make the determination of which sleep stage a person's in?
I had to basically scan, the websites for, you know, manuals, white papers, you know, FAQs for each website. Unfortunately I don't have the specific methodologies, but there is enough information to know, that there are, certain, physiological measures that, these devices use.
All of these consumer devices use heart rate and heart rate variability and movement, and Oura Ring is unique in incorporating some respiration and temperature as well. So I'll go into a little bit of details of, how these consumer wearables may be utilizing this data to differentiate sleep stages.
Also, these four, actually three of the four devices also provide a sleep score, which goes from one to a hundred, I think it's one to hundred, not zero to 100 and they all have their own formulas. And again, I don't have access to how these formulas were established or even created, and what type of preliminary work has been done to, to establish these scores.
But what I do know is that Garmin, for instance, uses, a sleep duration, which is adjusted for age, sleep architecture, time spent in Wake, nREM, and REM. And then they also incorporate some autonomic nervous system changes, particularly heart rate and heart rate variability. Then they also assess for restlessness, which is based on the number of times a person's awake at night and also the amount of movement.
Now, Fitbit, I wasn't able to get as much information, but I do know that they incorporate sleep duration, sleep architecture with, time in deep and REM sleep. There's heart rate involved and then movement as well. And Oura has what they call seven factors that come into their sleep score. Three of them has to do with sleep duration, so total sleep time, sleep efficiency and latency.
And also, two of them, the additional two is time in deep sleep and time in rem. And then interestingly, they have a midpoint of the sleep timing, which also goes into the sleep score, which is different than the other consumer wearables. And then the final seventh one is restfulness, which they used as their term instead of restlessness.
It has to do with a composite score based on the number of times a person wakes up, the amount of movement and getting out of bed. So, the, the seven factors were three here, two, one here one. So it adds up to seven. So this is, what, The, these three of the four, devices provide a sleep score from zero to a hundred.
I often get a score of like 60 to 70 on my Garmin, and I never understood how I, why it’s so bad. It would be great to figure out what, what are the components that's contributing to my poor score, but they don't provide that. But this will hopefully give you an idea how the sleep score is arrived at or derived.

Course episodes

Sleep 5.1 How Consumer Wearables Measure Sleep Quality

Sleep 5.2 Heart Rate, HRV, and Muscle Activity During Sleep

Sleep 5.3 Respiration & Temperature Monitoring with Wearables

Sleep 5.4 Challenges in Using Wearable Devices for Accurate Sleep Monitoring