An ambitious stroke prevention study tests the Apple Watch’s promise in health

Currently, millions of people with an irregular heartbeat are told to take expensive blood thinners, which prevent strokes, but also increase the risk of dangerous bleeding. A new study will investigate whether Apple Watches can be used as part of a strategy to minimize use of those medications when they’re not needed.

The seven-year study, expected to launch next spring, will compare strokes, bleeding, and health care cost outcomes between people who are given the standard course of blood thinners and an experimental group that will be directed to take medication only after an Apple Watch detects prolonged atrial fibrillation. 

“For many of us physicians who primarily take care of patients, we see the inadequacies of some of the treatment recommendations,” said Rod S. Passman, a principal investigator of the study and director of the Center for Arrhythmia Research at Northwestern University. In his practice he observed that while blood thinners help many patients, others get no benefit and are exposed to danger. “The concept of targeting individuals during high-risk periods grew out of that experience,” he said. 


The study, which has secured $37 million in funding from the National Heart, Lung, and Blood Institute, aims to enroll 5,400 participants. The American Heart Association, Johns Hopkins, Stanford, and the University of California, San Francisco, are also partners on the study, which will focus on a relatively low-risk population of people who don’t have a history of stroke, congestive heart failure, or other conditions.   

If the experimental arm of the study can prevent strokes as well as the standard of care and reduce instances of bleeding, it would be a major advance for cardiac care. It would also be a coup for Apple, which for years has been developing — and aggressively marketing — features that detect irregular heart rhythms in individuals but has yet to show they can directly impact care and improve outcomes. An upcoming version of Apple’s iPhone software also has a feature to help users manage their medications.


Apple will donate devices to the project and is assisting in the development of the study application. As part of that work, the company is helping researchers build a custom algorithm for the study, which will check the heart rhythm of participants much more frequently than the algorithm available to the general public. Upon detecting atrial fibrillation that lasts several hours, patients will be directed by the software to take blood thinners until the highest risk of stroke has passed, rather than being left on the drugs indefinitely. Passman was careful to emphasize that the intervention will be automated. 

“This does not require a physician to oversee it — that’s not scalable,” said Passman. He likened the experience to people with diabetes managing their insulin, who don’t need to call their doctor every time they check their blood sugar.

Passman said his group first began talking to Apple years ago, before Apple released the first version of its irregular heart notification feature. He said that researchers have known that atrial fibrillation and stroke risk fluctuate over time. But before new, fast-acting anticoagulants hit the market, and before technology made it possible to continuously monitor heart rhythm, there wasn’t much doctors could do with that information to change patient care. Prior to the new study, which is called Rhythm Evaluation for AntiCoagulaTion, or REACT-AF, Passman collaborated on two pilot studies that used implantable devices to detect when blood thinners are necessary. Both saw dramatic reductions the amount of time on medication.

Implantable devices would prove challenging to scale, given the cost and infrastructure needed to use them. But widely distributed products like the Apple Watch could get  the technology in the hands of more people.

One key question will be how reliably and accurately the new algorithm being used for the study can catch instances of A-fib. For the algorithm used in the Apple Watch available to the general public, the company’s studies show 88.6% sensitivity in detecting people who have irregular heart rhythms, according to documents published by the Food and Drug Administration. Those data are an important reminder of how the accuracy of consumer wearables can impact any intervention using them at scale.

“On a population level, the sensitivity does mean that some irregular rhythms could be missed,” said Sanket Dhruva, cardiologist and assistant professor of medicine at UCSF who is currently leading a study of the Apple Watch’s impact on health care utilization.

Nevertheless, for Passman, research like the new study is a key proving point for wearables.

“The advent and release of these technologies has outpaced the scientific research to show that the availability of these technologies actually saves lives and improves the quality of life,” said Passman. “This is a real, important example of the partnership between the consumer grade electronics companies and the medical community to show that these aren’t just gadgets for the consumer, but they can actually help guide health care.”

Harlan Krumholz, a cardiologist at Yale not associated with the study, agreed that it “is just what we need to validate a lot of assumptions about how digital tools can improve health.” Krumholz said what’s important is that the team is testing not just hardware or software but a whole strategy to process data and turn it into actionable information for clinicians and patients.

“These digital health interventions are often quite complex and so it is critical, as they are doing, to test the whole package,” he said.

Source: STAT