Made the graph using Python.

x = 4-stage kappa vs PSG
e = |TST_tracker – TST_PSG|
y = max(0, 100 – (100/60) × e)

So right = better staging, up = lower sleep time error, top-right = closest to PSG.
Data is from published PSG validation studies in 2022, 2024 and 2025.

Posted by Impressive_Suit4370

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12 Comments

  1. Wow, really thought Whoop was a gold standard… shows how much marketing can make your company’s perception.

  2. cheeze_whizard on

    I’m confused about the S8 (2024) and S8 (2025). The S8 came out in 2022. The S10 came out in 2024, and S11 in 2025. What do these two dots represent?

  3. What is the Garmin being used? 

    I know mine seems quite accurate, definitely for length, which seems like something I can more or less verify myself

  4. If you put all of their names next to their dots in the graph, why have a redundant legend on the side?

  5. ZipTheZipper on

    I was hoping to see how Samsung devices compare. They’ve been advertising their sleep tracking capabilities recently.

  6. Does this mean that Apple S8 has somehow gotten significantly worse from 2024 to 2025?

    What did they do to it?

  7. budgefrankly on

    There’s a guy doing a post-doc in bioinformatics (at least he was) that started a YouTube channel called “The Quantified Scientist” where he would wear medical-grade monitoring gear from his lab, and use it to evaluate the performance of smart-watches on heart-rate monitoring, sleep accuracy and other things.

    It’s really good, the only place I’d go for a Smart Watch review. Here’s a recent video looking at 15 wearables over 100 nights of sleep: https://www.youtube.com/watch?v=i4DByTQIRyY

    The summary is that many smart-watches aren’t good at detecting short-term spikes in heart-rate, and — at least a couple of years ago — most were shockingly bad at monitoring sleep.

    The only one that got good marks across the board was the Apple Watch, and even then it’s blood-oxygen monitoring looked shaky.

  8. What software was tracking the sleep progress on the watch? Default OS? 3rd party like Sleep as Android?

  9. So most of them are actually useless if you want to know more than what your actual sleep time was.

  10. Lord_of_magna_frisia on

    I use the body battery function to monitor sleep quality and most of time it correlates with my feeling how my sleep quality was