Smartwatches have gotten pretty good at detecting atrial fibrillation, the most common heart rhythm disorder in the world, affecting nearly 38 million people globally. But many people brush off the alert, assuming that if they feel fine, it probably isn’t a big deal. New research presented at EHRA 2026 in Paris suggests that’s a mistake worth reconsidering.
The study is a post-hoc analysis of two large Swedish screening programs, STROKESTOP and STROKESTOP II, in which adults aged 75 to 76 were screened for atrial fibrillation using an ECG. Researchers tracked participants for several years to see who went on to develop heart failure.
The numbers are hard to ignore. In STROKESTOP, about 23% of people whose atrial fibrillation was caught through screening later developed heart failure. STROKESTOP II returned a similar figure of around 20%.
What does this have to do with your smartwatch?
If you have ever watched any Apple Watch keynote video, you know Apple likes to showcase how its smartwatch is helping people avoid heart attacks thanks to its atrial fibrillation (AF) detection feature.
Apple Watch is not the lone smartwatch doing this. Most modern smartwatches can detect atrial fibrillation, quietly, in people who feel perfectly fine and have no obvious symptoms. This research shows that asymptomatic does not mean harmless.
People with screening-detected atrial fibrillation had roughly three times the heart failure risk compared to those without atrial fibrillation.
Why should you act on it fast?
Heart failure showed up within six months of atrial fibrillation detection in both studies. That’s a short window, and it makes the case for treating a smartwatch alert as a reason to see a doctor sooner rather than later.
Doctor Gina Sado from Danderyd Hospital in Stockholm, who led the research, noted that atrial fibrillation and heart failure accelerate each other, and catching both early gives patients the best chance at managing both conditions effectively.
So when your smartwatch gives you an AF warning, it’s probably a good idea to consult your doctor. At worst, nothing is wrong, and you pay for a checkup. But in most cases, it will prevent a scary health condition.
