Stanford Medicine has published more details about the future of the Heart Study program it conducted in partnership with Apple, in which it attempted to reliably detect atrial fibrillation in Apple Watch wearers.

The condition, which is characterized by an irregular heartbeat, often remains hidden because many people don't experience symptoms. Atrial fibrillation can increase the risk of stroke and heart failure.

apple heart study
According to Stanford, the study involved 400,000 participants, making it the largest screening program for atrial fibrillation ever conducted. A paper has also been published in the American Heart Journal describing the unique design of the clinical trial.

Enrollment began in late 2017 and closed in August. Although some participants were informed in September that their participation in the study was complete, Stanford says it will continue to collect and collate data until early next year, which is consistent with Apple's original announcement.

"We hope this study will help us better understand how wearable technologies can inform precision health," said Lloyd Minor, MD, dean of the School of Medicine. "These new tools, which have the potential to predict, prevent and manage disease, are finally within our reach."

The FDA cleared two Apple Watch medical apps in September. One app uses data from the Apple Watch Series 4 to take an ECG by touching the button on the side of the device. The second app uses data from an optical sensor available on the Apple Watch Series 1 and later to analyze pulse data and identify irregular heart rhythms indicating atrial fibrillation. The Apple-Stanford Heart Study used the second app.

Each year in the United States alone, atrial fibrillation results in 130,000 deaths and 750,000 hospitalizations, according to the Centers for Disease Control and Prevention. The CDC estimates that the condition affects between 2.7 million and 6.1 million people. In addition, another 700,000 people may have undiagnosed atrial fibrillation.

Top Rated Comments

Veinticinco Avatar
95 months ago
Even though cardiology isn’t my field, it will be very interesting to see the first data analysis.
[doublepost=1541159489][/doublepost]Far from being a niche product, the AW’s health monitoring potential is seismic. Blood glucose monitoring would be the next hurdle and game-changer.
Score: 6 Votes (Like | Disagree)
centauratlas Avatar
95 months ago
Even though cardiology isn’t my field, it will be very interesting to see the first data analysis.
[doublepost=1541159489][/doublepost]Far from being a niche product, the AW’s health monitoring potential is seismic. Blood glucose monitoring would be the next hurdle and game-changer.
Other game changers:
1. Using the optical sensor (perhaps an improved version) to monitor blood oxygen saturation.
2. Continuous body temperature monitoring. Your watch could know that your "normal" body temperature is 98.2 in the morning and 98.9 in the afternoon or whatever. You'd have months/years of data to say, okay, my temp is 0.4 above normal right now, perhaps I should go to bed earlier so that when I am sick in the morning, I'll be well rested.
...and many more.

While in many controlled cases these are done (e.g. hospitals) I don't believe there have been any long term studies of large groups (e.g. 400,000 people!) where this data is collected. You might see a slight spike (e.g. a tenth of a degree) in temperature a day or two before a cold or flu hits. Or you might see a drop in oxygen sat level by 1% or 2% days before pneumonia is visible on an x-ray.

With half a million people, this type of information could become visible in the data and could then be used going forward.

There are many other uses where continuous data (or even 12-18 hours a day) monitoring can provide important information for doctors and consequently patients.

One hopes the FDA (and equivalent agencies around the world) don't stand in the way of out-of-the-box uses.
Score: 3 Votes (Like | Disagree)
bbednarz Avatar
95 months ago
This is absolutely amazing that Apple hasn’t moved this from a fashion accessory to a true health and fitness device
This has been pitched as a health and fitness device since the Series 2 debuted. The original watch was the only one that was really mainly focused on the fashion side. They changed course since then and now the main thing they pitch is health and fitness. Elevated heart rate notifications, EKG, fall detection, closing your rings: these are the main things they talk about when discussing the watch. It still has some fashion in it with the different casings and bands, but all of the functions of the watch are still present in all casing options.
Score: 3 Votes (Like | Disagree)
keysofanxiety Avatar
95 months ago
That is a massive study. You can tell Apple are taking this seriously.

I’ve only had my Apple Watch for less than a fortnight and I can already tell how often I’ll be using it.
Score: 2 Votes (Like | Disagree)
velocityg4 Avatar
95 months ago
That is a massive study. You can tell Apple are taking this seriously.

I’ve only had my Apple Watch for less than a fortnight and I can already tell how often I’ll be using it.
Of course they would. Just think of the sales boon if these were recommended by doctors and covered by health insurance/government healthcare around the world. Perhaps make a much more advanced $50,000 model for use in hospitals for patient monitoring and diagnostics.
Score: 1 Votes (Like | Disagree)

Popular Stories

wwdc sans text feature

Apple Rumored to Announce New Product on February 19

Thursday February 5, 2026 12:22 pm PST by
Apple plans to announce the iPhone 17e on Thursday, February 19, according to Macwelt, the German equivalent of Macworld. The report, citing industry sources, is available in English on Macworld. Apple announced the iPhone 16e on Wednesday, February 19 last year, so the iPhone 17e would be unveiled exactly one year later if this rumor is accurate. It is quite uncommon for Apple to unveil...
maxresdefault

Apple Shows Off a Key Reason to Upgrade to the iPhone 17

Saturday February 7, 2026 9:26 am PST by
Apple today shared an ad that shows how the upgraded Center Stage front camera on the latest iPhones improves the process of taking a group selfie. "Watch how the new front facing camera on iPhone 17 Pro takes group selfies that automatically expand and rotate as more people come into frame," says Apple. While the ad is focused on the iPhone 17 Pro and iPhone 17 Pro Max, the regular iPhone...
Apple Logo Zoomed

Tim Cook Teases Plans for Apple's Upcoming 50th Anniversary

Thursday February 5, 2026 12:54 pm PST by
Apple turns 50 this year, and its CEO Tim Cook has promised to celebrate the milestone. The big day falls on April 1, 2026. "I've been unusually reflective lately about Apple because we have been working on what do we do to mark this moment," Cook told employees today, according to Bloomberg's Mark Gurman. "When you really stop and pause and think about the last 50 years, it makes your heart ...
Finder Siri Feature

Why Apple's iOS 26.4 Siri Upgrade Will Be Bigger Than Originally Promised

Friday February 6, 2026 3:06 pm PST by
In the iOS 26.4 update that's coming this spring, Apple will introduce a new version of Siri that's going to overhaul how we interact with the personal assistant and what it's able to do. The iOS 26.4 version of Siri won't work like ChatGPT or Claude, but it will rely on large language models (LLMs) and has been updated from the ground up. Upgraded Architecture The next-generation...
iOS 26

iOS 26.3 and iOS 26.4 Will Add These New Features to Your iPhone

Tuesday February 3, 2026 7:47 am PST by
While the iOS 26.3 Release Candidate is now available ahead of a public release, the first iOS 26.4 beta is likely still at least a week away. Following beta testing, iOS 26.4 will likely be released to the general public in March or April. Below, we have recapped known or rumored iOS 26.3 and iOS 26.4 features so far. iOS 26.3 iPhone to Android Transfer Tool iOS 26.3 makes it easier...