Your watch says you have heart disease. What now?

Just because your smartwatch can tell you if you have an irregular heartbeat, does that mean the information will help you?

Many new smartwatches, including those from Apple, have sensors that can pick up an irregular heart rate and alert users that they may be in atrial fibrillation, or AFib. The devices hit the market at a time when consumers are becoming interested in tracking aspects of their health beyond fitness.

AFib is an irregular and often fast heart rhythm that can cause blood clots in the heart; if blood clots break loose, they can travel to the brain and cause a stroke. People often don’t even know they have the condition until disaster strikes, cardiologists say.

About one in five American adults say they regularly wear a smartwatch or fitness tracker, according to the Pew Research Center. At least 20 smartwatches sold in the US currently have the ability to detect irregular heart rhythms, says market research firm IDC.

Some doctors caution that smartwatches and other AFib-detecting wearable devices are not proven screening tools, saying alerts for non-severe cases can result in anxiety for patients, expensive tests and unnecessary treatment. Others say the people who could benefit most from the devices aren’t wearing them — and may not be able to afford them.

“It is very possible that atrial fibrillation can be detected in high-risk patients, but has it been shown to reduce the number of strokes in any study? No, and it certainly has not been shown to reduce death,” says NA Mark Estes, professor at the University of Pittsburgh School of Medicine and an expert in the American Heart Association.

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supports studies on the effectiveness of such monitoring, but they are ongoing.

Risk of overdiagnosis

The problem with using smartwatches to detect AFib is that they tend to be worn by younger people, cardiologists say. According to Pew, the majority of people who wear smartwatches and fitness trackers are between the ages of 18 and 49. Only 2% of Americans under 65 have AFib, while 9% of people 65 and older have it, according to Pew. Centers for Disease Control and Prevention.

Even for older adults, the benefits are not clear. The US Preventive Services Task Force, an independent panel of experts in evidence-based medicine, said earlier this year that there is insufficient evidence to weigh the benefits of AFib screening for asymptomatic adults over 50.

There may be stronger benefits to tracking AFib episodes among people already diagnosed with the condition, says Dr. Estes. In a September software update, Apple introduced a way for AFib patients to use newer model Apple Watches to track when their episodes occur and how long they last. They can also track how they relate to sleep problems, alcohol consumption or lack of exercise.

An Apple spokeswoman says the information can motivate wearers to make lifestyle changes.

But let’s say you’re a relatively young, healthy person whose watch tells you you might have AFib. Your doctor will need to run tests to confirm the watch’s results – the whole process causes you anxiety.

With Apple’s WatchOS 9, people who have been diagnosed with atrial fibrillation can now track their history.


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If AFib is confirmed, then what? Blood thinners are a common AFib treatment. But blood thinners cause some people to avoid injury by reducing physical activity — activity that might otherwise keep them fit and protected against heart disease, says Daniel Capurro, deputy director of the Center for Digital Transformation of Health at the University of Melbourne. Overreacting to a scary diagnosis can lead to heart problems instead of relieving them.

Dr. Capurro – who wrote an opinion piece published in February on the dangers of digital overdiagnosis in the Journal of the American Medical Association – points to lessons from early prostate screening. A blood test led to several men being diagnosed and treated for a slow-growing cancer that may never have harmed them. Radiation therapy or surgery for prostate cancer can result in urinary incontinence and impotence. “Many years later, we saw that we had had little impact on health outcomes, and we were harming many men,” says Dr. Capurro.

As with cancer, an AFib diagnosis can also make it harder and more expensive to get health or life insurance, adds Dr. Capurro.

Benefits of early detection

Some doctors say that AFib-detecting smartwatches — which generally cost between $100 and $400 — are not reaching the population that could actually benefit from them.

Among the people most at risk are lower-income patients who lack access to high-quality medical care. Cardiologists studying the benefits of smartwatches in early AFib detection say they need to be aware of how accessible such devices are.

Rod Passman, director of the Center for Arrhythmia Research at Northwestern University in Chicago, is conducting a long-term study to track AFib episodes. Apple provides watches. He is involved in another study with Johnson & Johnson and Apple to determine whether early AFib detection with Apple Watches can reduce the risk of stroke and other cardiovascular conditions.

If studies show that wearable devices can improve patient outcomes, healthcare costs could decrease, says Dr. Passman, who says he receives no funding from Apple. “If an insurance company will pay for your blood thinners and stroke, maybe one day they’ll pay for your Apple Watch,” he says.

Google-owned Fitbit offers several AFib detection models, including this $230 Versa 4.


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Marco Perez, associate professor of medicine at Stanford University, co-led an Apple-funded study from November 2017 to February 2019 on detecting irregular heart rhythms. He says early detection in seemingly low-risk people can help identify other heart problems.

“A young person shouldn’t have an AFib reading unless there’s something else going on,” says Dr. Perez. “I’ve had patients come in with these messages, and when we did an ultrasound, we found other conditions like cardiomyopathy.” Cardiomyopathy, a heart muscle disease, can be treated with medication.

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But, he adds, there are no long-term studies showing that patients are generally better off with early detection and intervention.

Dr. Perez said Apple’s heart study found few false positives because of the way the detection algorithm was designed. The wearer is not notified until five out of six consecutive checks detect an irregular heart rate consistent with AFib.

Fitbit recently completed a study on AFib detection using its devices and found similarly low rates of false positives.

Tony Faranesh, a researcher at Fitbit, acknowledges that the wearables industry is still in the early days of understanding how useful its devices can be in detecting cardiovascular irregularities.

“This is not a diagnosis,” Mr. Faranesh says of the AFib announcement. “It’s a way to identify early signs of disease and start a conversation with your doctor.”

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Write to Julie Jargon at Julie.Jargon@wsj.com

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