Most Apple Watch users won’t get health benefits from AFib detection, study finds

By Nicole Wetsman  Mar 2, 2022, 4:19pm EST

Photo by Vjeran Pavic / The Verge

One promised benefit of the Apple Watch is early detection of a heart condition called atrial fibrillation, a type of irregular heart rhythm. But most people who wear the watch are in a demographic that wouldn’t actually be able to do much with that information, according to a new study — most doctors wouldn’t prescribe them the medication usually given for that condition, which is usually detected in older people.

Getting an alert about a heart rhythm, then, doesn’t help the typical Apple Watch user’s overall health, says study author Josh Pevnick, co-director in the division of informatics at Cedars-Sinai Medical Center in Los Angeles. “It can cause anxiety for people who it identifies, and if there’s no treatment, then you’re maybe not bringing much benefit,” he says.

Most research on the health features on wearable devices has focused on whether they can accurately identify a potential problem — like atrial fibrillation, which Apple, Fitbit, Withings, and Samsung watches are Food and Drug Administration-cleared to detect. But detecting an issue is different from being able to do something about it. This new study indicates that, in most cases, doctors wouldn’t do much if atrial fibrillation is flagged, which has Pevnick and other researchers wondering about how useful that information is to patients.

People with atrial fibrillation are at higher risk of strokes and are often prescribed blood thinners to knock that risk down. But not everyone with the heart rhythm issue qualifies for blood thinners — they’re not typically used for younger people without other factors that could increase stroke risk, Pevnick says. And most Apple Watch users at the Center fell into that latter category.

“Most of the people who are connecting their devices wouldn’t have anticoagulants recommended anyway, even if they were found to have atrial fibrillation, so it wasn’t going to change any prescribing,” he says.

Cedars-Sinai Medical Center has a program that lets patients connect their Apple Watch data with their electronic medical record. For this study, published in February in the Journal of the American Medical Informatics Association, the research team looked at the Apple Watch and clinical data (like medication history and demographics) from around 1,800 patients.

The study didn’t look at how many people actually got an irregular heartbeat alert. But they found that only 0.25 percent of people wearing an Apple Watch at the Center would qualify for anticoagulants if they had atrial fibrillation flagged by the device.

Pevnick says the findings show that the typical Apple Watch user (or at least the typical Apple Watch user who agrees to share their data with their electronic health record) isn’t the group that doctors are most concerned about — especially when it comes to atrial fibrillation. “If you’re trying to provide some health benefits for people in terms of identifying atrial fibrillation, the key is probably to make sure you identify the right people,” he says. “You may need to go out and seek out the people who would benefit.”

The study also highlights the way Apple Watch and other consumer-focused quasi-medical devices opened new questions for doctors to try and address. Most of the time, atrial fibrillation is detected in older people who do qualify for medication to address the risks it poses. But the introduction of smartwatch tools that can detect abnormal heart rhythms has created a new category of younger, healthier people who are getting flagged for potential issues. Doctors still don’t know the best way to handle that group, Pevnick says.

“We’re picking up a different kind of atrial fibrillation,” he says. “It’s different from what has been studied before.”