Over 2,000 Participants Received Irregular Heart Rhythm Notification in Apple Watch Study

Stanford Medicine researchers presented their findings of the Apple Heart Study at the American College of Cardiology's 68th Annual Scientific Session and Expo in New Orleans today, as noted by Apple in a press release.

apple heart study
Apple and Stanford created the study to evaluate the Apple Watch's irregular heart rhythm notification feature, which occasionally checks the wearer's heart rhythm in the background and sends a notification if an irregular heart rhythm appears to be suggestive of atrial fibrillation.

419,093 people across the United States participated in the study. As part of the study, if an irregular heart rhythm was identified, participants received a notification on their Apple Watch and iPhone, a phone consultation with a doctor, and an ECG patch for additional monitoring.

Study results showed 0.5 percent of participants - approximately 2,095 people - received an irregular heart rhythm notification. Apple says "many participants sought medical advice following their irregular rhythm notification."

Apple COO Jeff Williams:

We are proud to work with Stanford Medicine as they conduct this important research and look forward to learning more about the impact of Apple Watch alongside the medical community. We hope consumers will continue to gain useful and actionable information about their heart health through Apple Watch.

Apple announced the Heart Study in collaboration with Stanford back in November 2017 and stopped accepting new participants in August 2018.

Related Roundup: Apple Watch 11
Buyer's Guide: Apple Watch (Buy Now)

Popular Stories

iPhone Pocket Short

iPhone Pocket is Now Completely Sold Out Worldwide

Tuesday November 25, 2025 7:16 am PST by
Apple recently teamed up with Japanese fashion brand ISSEY MIYAKE to create the iPhone Pocket, a limited-edition knitted accessory designed to carry an iPhone. However, it is now completely sold out in all countries where it was released. iPhone Pocket became available to order on Apple's online store starting Friday, November 14, in the United States, France, China, Italy, Japan, Singapore, ...
New Intel Logo

Apple and Intel Rumored to Partner on Mac Chips Again in a New Way

Friday November 28, 2025 7:33 am PST by
While all Macs are now powered by Apple's custom-designed chips, a new rumor claims that Apple may rekindle its partnership with Intel, albeit in a new and limited way. Apple supply chain analyst Ming-Chi Kuo today said Intel is expected to begin shipping Apple's lowest-end M-series chip as early as mid-2027. Kuo said Apple plans to utilize Intel's 18A process, which is the "earliest...
iphone black friday gold

The Best Black Friday iPhone Deals Still Available

Friday November 28, 2025 6:24 am PST by
Cellular carriers have always offered big savings on the newest iPhone models during the holidays, and Black Friday 2025 sales have kicked off at AT&T, Verizon, T-Mobile, and more. Right now we're tracking notable offers on the iPhone 17, iPhone 17 Pro, iPhone 17 Pro Max, and iPhone Air. For even more savings, keep an eye on older models during the holiday shopping season. Note: MacRumors is...
apple store down feature

Here's Why the Apple Store is Going Down

Thursday November 27, 2025 1:01 pm PST by
Apple's online store is going down for a few hours on a rolling country-by-country basis right now, but do not get your hopes up for new products. Apple takes its online store down for a few hours ahead of Black Friday every year to tease/prepare for its annual gift card offer with the purchase of select products. The store already went down and came back online in Australia and New Zealand, ...
streaming black friday 2025

Best Black Friday Streaming Deals - Save Big on Apple TV, Disney+, Hulu, and More

Thursday November 27, 2025 1:14 pm PST by
We've been focusing on deals on physical products over the past few weeks, but Black Friday is also a great time of year to purchase a streaming membership. Some of the biggest services have great discounts for new and select returning members this week, including Apple TV, Disney+, Hulu, Paramount+, Peacock, and more. Note: MacRumors is an affiliate partner with some of these vendors. When...
iphone air camera

iPhone Air Flop Sparks Industry Retreat From Ultra-Thin Phones

Thursday November 27, 2025 3:14 am PST by
Apple's disappointing iPhone Air sales are causing major Chinese mobile vendors to scrap or freeze their own ultra-thin phone projects, according to reports coming out of Asia. Since the ‌iPhone Air‌ launched in September, there have been reports of poor sales and manufacturing cuts, while Apple's supply chain has scaled back shipments and production. Apple supplier Foxconn has...
maxresdefault

The MacRumors Show: Apple's Big Plans for iPad Mini 8

Friday November 28, 2025 8:39 am PST by
On this week's episode of The MacRumors Show, we talk through the latest rumors about Apple's upcoming iPad mini 8. Subscribe to The MacRumors Show YouTube channel for more videos The next-generation version of the iPad mini is expected to feature an OLED display, as part of Apple's plan to expand the display technology across many more of its devices. Apple's first OLED device was the Apple...
Cyber Monday Deals 2025

Best Cyber Monday Apple Deals Include Big Discounts on AirPods, Apple Watch, and More

Sunday November 30, 2025 7:33 am PST by
Now that Black Friday is in the rearview mirror, Cyber Monday discounts have begun appearing online, and you can find popular Apple products like AirPods, iPad, Apple Watch, and more at all-time low prices. In this article, the majority of the discounts will be found on Amazon. Note: MacRumors is an affiliate partner with some of these vendors. When you click a link and make a purchase, we may ...

Top Rated Comments

GubbyMan Avatar
88 months ago
So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?
Score: 31 Votes (Like | Disagree)
ThunderSkunk Avatar
88 months ago
A couple times a month I get a few dropped heartbeats and some fluttering around for a bit while I wonder if this is finally it. But every time, it ends in disappointment. I still have to get up the next day and go to work to prop up this barbaric culture for absolutely no good reason.
Score: 18 Votes (Like | Disagree)
DoctorTech Avatar
88 months ago
No medical screening test is 100% accurate. Early pregnancy tests are about 99% accurate. Even mammogram screening for breast cancer is only 87% accurate https://ww5.komen.org/BreastCancer/AccuracyofMammograms.html

Most people in the medical community agree it is better to have a false positive than a false negative because a false negative would discourage someone from seeking medical treatment and could ultimately lead to worse effects than someone seeking medical treatment for a condition they do not have.

For such a new, low cost, and non-intrusive device, I think the results of this study are actually pretty amazing.
Score: 12 Votes (Like | Disagree)
KPandian1 Avatar
88 months ago
Irregular rhythm happens everyday, even by narrow medical definition; there is variation even with breathing.

The irregularity detected here is reported "if an irregular heart rhythm appears to be suggestive of atrial fibrillation." The software is setup by a medical team with oversight to eliminate the daily variations - A Fib is characteristically different. Even on a 12-lead ECG with Holter monitoring, the interpretation is physician based, preferably a cardiologist.

So, if 200-20 or even 2 of these detected were found with real atrial fibrillation rhythm, it is a win; these are from people with no known heart problems.

The worst a false positive does is send someone for further rhythm monitoring by a pro - worth the hassle.

The first post is sarcasm.
Score: 11 Votes (Like | Disagree)
Khedron Avatar
88 months ago
So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?
34% were confirmed to have atrial fibrillation with a follow-up.

Not all the other 66% would be false positive since it's an intermittent condition.
Score: 9 Votes (Like | Disagree)
kpeex Avatar
88 months ago
So what did this lead to? 0.5% got the notification and then what? Did they all really have irregular heart rhythm or were there false positives?
I enrolled on the first day that the AHS app was available to the public. From the app, I had 3,144 data contributions in 459 days. As info, I cycled about 6,000 miles during that period, probably about half those days. My heart rate normally goes way up when cycling. RHR tends to be kind of low. I received an "Irregular Heart Rhythm Observed" notification about 45 days into the study:

* I initiated an in-app video call to an AHS cardiologist using the direct link on the notification that popped up. She interviewed me for about 30 minutes. During the interview, she discussed the study as having flagged me for single digit number of SVT events during five different 60-second measurement periods. (Supra-ventricular Tachycardia)
* They overnighted a 7-day ambulatory ECG monitor that I returned at the end of the week.
* When the results were ready, they notified me and sent another in-app video call link.
* A second video conference explained the results -- a few more instances of SVT detected. She recommended that I follow-up with a cardiologist, who was provided the monitor results. I also got pdfs of all records.
* I went to a locally recommended cardiologist, who discussed the SVT events that the watch and monitor picked up.
* He recommended I have an echocardiogram done to establish a baseline, which I did.
* There was a follow-up to discuss the results.

I guess it wasn't a false positive and it wasn't A-fib. The cardiologist seemed surprised that a fitness tracker caught it.
Score: 9 Votes (Like | Disagree)