Apple study finds Watch can detect more types of irregular heartbeats


New findings from the Apple Heart Study indicate that Apple Watches can identify irregular heartbeats other than atrial fibrillation arrhythmias.

Funded by Apple and conducted by researchers from the Stanford University School of Medicine, the study has been ongoing since 2017. It has enrolled 419,297 Apple Watch and iPhone owners across the U.S. to study the company’s irregular heart rate-detecting algorithm.

Previous results from the study showed Apple Watch’s irregular pulse detection algorithm successfully detects atrial fibrillation in 84% of people who receive a notification. The new investigation, published this week in the American Heart Association’s Circulation Journal, sought to find the prevalence of other forms of arrhythmias detectable by the Apple Watch.


Among participants that received an irregular heartbeat notification on their Apple Watch, but who didn’t have atrial fibrillation upon electrocardiogram (ECG) reading, 40% had another form of arrhythmia.

The most common arrhythmias detected were premature atrial contractions, premature ventricular contractions, atrial tachycardia and nonsustained ventricular tachycardia, according to the study.

Additionally, the researchers found that almost a third of participants that were notified of an arrhythmia, but didn’t have atrial fibrillation on the subsequent ECG reading were eventually diagnosed with atrial fibrillation later in the study. This signals that the Apple Watch could have been detecting early signs of atrial fibrillation that the ECG patch missed.

The researchers say that defining care options for patients with arrhythmias other than atrial fibrillation “is important as AF detection is further investigated, implemented, and refined.”


Once consent was given, participants’ smartwatches began passively measuring their heartbeat intervals in search of recurring irregularities. If found, participants received an irregular pulse notification, and their measurements were then compared against ECG patch readings.

Participants with irregular heartbeats were prompted to complete a series of telehealth appointments with the researchers to assess symptoms and discuss the readings.

Of all the participants in the Apple Heart Study, 2,161 received an irregular pulse notification. Four hundred and fifty of them returned an analyzable ECG patch and 297 (66%) of these had no atrial fibrillation detected – making them the study’s cohort.

These participants were primarily male (71%) and white (85.2%). The average age was 57.7 years old.


By now, Apple is a major contributor to health research. Besides its heart study with Stanford, researchers have used Apple Watch’s heart rate measuring features to study heart rate variability changes prior to COVID-19 diagnosis.

Apple and Harvard’s T.H. Chan School of Public Health collaborated on the Apple Women’s Health Study that studies menstrual cycle characteristics. Preliminary data showed that period symptoms were felt similarly across demographics, with abdominal cramps being the most common symptom.

The tech giant is in the midst of a two-year study on asthma with Anthem, UC Irvine and software company CareEvolution. The study is looking to help patients control their asthma and reduce hospital utilization.

Last year, Apple and UCLA kicked off their study to see how sleep, physical activity and heart rate relate to depression and anxiety.

This year, on World Hearing Day, Apple and the University of Michigan shared preliminary data from the Apple Hearing Study. Results showed that a significant number of people are putting themselves at risk for hearing loss.




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