Apple has been sharing more about the blood pressure “measurement” feature on the Apple Watch, explaining how it works and pointing to related studies. Back in a 2024 article, we talked about the challenges of testing wearables and their health features, noting that these studies are public and accessible. While they can be tricky for non-experts, knowing a few basics helps make sense of them—like a recent Apple study on the hypertension notification for the Watch. To clarify, this isn’t a full blood pressure reading that shows exact numbers after calibration or with a cuff. It’s a screening tool meant to flag if you might have high blood pressure.
Apple’s study trained the algorithm on 3,216 people, validated it with 3,878, and tested it on 2,236. They also broke down participants by weight groups, as is standard. The results highlight sensitivity and specificity. Sensitivity shows how well the test spots people who actually have the condition—here, it’s 41.2%, meaning less than half of those with hypertension get alerted. Specificity, at 92.3%, indicates how well it correctly identifies healthy people. These numbers are linked; tweaking the threshold changes them.
We won’t get too technical or compare to other products, but it’s worth noting that higher sensitivity in screenings like this is often better, even if it lowers specificity. A false positive just means a quick, harmless check with a standard blood pressure cuff—maybe even at home with an affordable one. We can’t say if the Apple Watch’s detection falls short due to sensitivity or technical limits, but it’s a reminder to stay informed.
What do you think about this feature? I’d love to hear your thoughts!
source: Apple
