Some of these trends aren’t new. For years, doctors have watched patients come into their offices after researching medical conditions online, Heaton said. Smartwatches, though, passively monitor people who aren’t necessarily looking for a diagnosis. And Apple isn’t the only company flagging users with what its products pick up as abnormal heart rhythms: Samsung’s Galaxy Watch 3 has an EKG feature, as does Fitbit’s Sense smartwatch. While the percentage of people who get an abnormal heart reading on one of these devices could be low (a study of the Apple Watch found that less than 1 percent of users had an alert), millions of people use these products — so there could still be thousands of additional people going to the doctor based on them.

These types of products “blur the line between rigorously-studied medical devices and wellness tools,” Wyatt said. People may not understand how well they actually work and what they should actually be used for. People who already have an atrial fibrillation diagnosis, for example, aren’t supposed to use the Apple Watch feature — but over 20 percent of the people in the Mayo Clinic study did have that diagnosis already. The feature also isn’t supposed to be used by anyone under 22 years old, but nearly two dozen people with records in the study were below that cutoff.

Smartwatches might be useful ways for people to monitor their health on their own, at home, but it’s still not clear what their utility could be. Most of the research done on the Apple Watch, for example, focuses on how well it can detect atrial fibrillation, but it doesn’t track how well it can actually be used as a screening tool in the context of the health care system. Without that information, doctors like Heaton worry that the devices could cause unnecessary confusion and stress for patients. “Understanding context and the nuances of illness is important and at this point cannot be fully understood purely by a wearable medical device,” she said.