In the name of “Sleep Science” I went to bed wearing two sleep trackers. At 3 AM, I opened my eyes and a little bit of anxiety kicked in. I wasn’t worrying about what surgery I had to perform in the morning; I was worrying about my Sleep Score.
I was suffering from Orthosomnia, which is the slightly sarcastic term used for individuals who actually sacrifice sleep due to the stress of trying to optimize their sleep data. And that gets to the point of this article. A wearable sleep report is not the same thing as a medical sleep study. Here’s why.
Medical Sleep Studies (PSG) uses what’s called an EEG. Wearables DO NOT. A real study uses an reads your brain waves and labels each stage. You get NREM and REM. You get actual arousals. You get signal quality that does not care about your wrist.
Wearables take a different path. They watch heart rate, movement, temperature, and breathing. Then, each company builds its own model of what “sleep” looks like. Different names. Different rules. Same signals. This is why the same night can look different depending on what wearable you are using.
You can also trick them. If you wake up and stay still, the watch may think you’re asleep. If your partner is thrashing around with the Jimmy Legs, your tracker might decide you are moving around a lot and score your sleep as terrible. It’s worth a watch if you don’t know what Jimmy legs are.
And that’s the point. These devices are making estimates based on movement. They can’t see brain waves. They can’t reliably tell obstructive apnea from central apnea. They can’t quantify snoring. They don’t measure real arousals. They guess.
The bottom line is these scores are estimates. They can’t see brain waves but recent validation studies on Oura, Whoop, and Apple Watch show a consistent trend:
Sleep/Wake: They are excellent at knowing when you are asleep (Sensitivity >90%).
Sleep Stages: They struggle to differentiate Light vs. Deep sleep (Agreement ~50-60%).
But wearables do some things better than a one-night sleep lab:
They track you night after night, identifying your baseline.
In late 2024, Apple and Samsung earned FDA clearance to flag sleep apnea risk, with Withings following in the EU.
They hold us accountable for bedtimes.
The bottom line is simple. Wearables are helpful. They are not sleep labs. And chasing a perfect score at 3 AM probably hurts sleep more than it helps. And if your partner has the Jimmy Legs, learn a lesson from Frank on Seinfeld, you may want to get a separate bed.
Have you ever woken up feeling fully rested, only to have your watch tell you that you slept terribly? Which one do you trust more, your body or the algorithm?
Below is a cross-device comparison of how each device names different sleep stages
Consistent Mapping for Distinct Sleep Stages
The most distinct and clinically significant sleep stages—Wake, Deep, and REM—show near-universal consistency in how they are tracked and named across consumer devices.
Wake Stage Consistency: All five consumer trackers map the PSG “Wake” stage (”Awake or tossing”) to a term synonymous with being awake, primarily using “Awake,” with Oura using the slightly more specific “Awake/WASO” (Wake After Sleep Onset).
Deep Sleep Terminology: The PSG stage “N3” (”Deep, restorative”) is consistently labeled as “Deep” by Apple, Oura, Samsung, and Elemind. WHOOP uses the more scientific term “Slow Wave Sleep (SWS)” to identify this stage.
REM Sleep Uniformity: The “REM” stage (”Dream sleep”) is identically labeled as “REM” across Apple, Oura, WHOOP, and Samsung, with Elemind using a slight variation, “Rem.”
References
de Zambotti M, et al. Validation of the Oura Ring for sleep staging compared with polysomnography. Sleep. 2017.
Carrier J, et al. Performance of Oura Ring Gen3 against EEG-based sleep staging. Nature and Science of Sleep. 2022.
Berryhill S, et al. Accuracy of the WHOOP wearable for sleep staging. Journal of Medical Internet Research. 2023.
Miller D, et al. Evaluation of sleep and recovery metrics from the WHOOP strap. Sensors. 2022.
Chinoy ED, et al. Apple Watch sleep detection compared with PSG and actigraphy. Sleep. 2023.
Apple Heart and Movement Study. Sleep measurement validation. npj Digital Medicine. 2024.
Lee J, et al. Sleep staging performance of the Samsung Galaxy Watch vs PSG. Journal of Clinical Sleep Medicine. 2024.
Samsung Sleep Apnea Detection. FDA 510(k) clearance documentation. 2024.
Withings Sleep Apnea Algorithm. EU MDR regulatory approval. 2025.
Chouchou F, et al. Multisensor sleep detection validation in Withings devices. Nature Digital Medicine. 2022.