Some smart wearables can interfere with pacemakers and other medical devices, according to researchers at the University of Utah.

Wearable devices such as smartwatches have proven to be invaluable companions for the health conscious. But a study from the University of Utah shows for a small group of people, some of these electronic fitness gadgets could possibly be risky to their health, even potentially deadly.

Electrical and computer engineering assistant Benjamin Sanchez Terrones and associate professor of medicine Benjamin Steinberg have published a study that shows wearable devices such as the Samsung Galaxy Watch 4, Fitbit smart scales or Moodmetric smart rings, among others, have sensing technology that could interfere with cardiac implantable electronic devices (CIEDs) such as pacemakers, implantable cardioverter defibrillators (ICDs), and cardiac resynchronisation therapy (CRT) devices.

“This study raises a red flag,” said Sanchez Terrones. “We have done this work in simulations and benchtop testing following Food & Drug Administration accepted guidelines, and these gadgets interfere with the correct functioning of the CIEDs we tested. These results call for future clinical studies evaluating the translation of our findings to patients wearing CIEDs and using these wearable devices.”

Their study was published in the scientific journal Heart Rhythm. The paper was authored by electrical and computer engineering graduate student Gia-Bao Ha, Sanchez Terrones, Steinberg, internal medicine professor Roger Freedman, and Universitat Autònoma de Barcelona cardiology professor Antoni Bayés-Genís.

At issue are specific wearable smartwatches, at-home smart scales and smart rings that use bioimpedance, a type of sensing technology that emits a very small, imperceptible current of electricity measured in microamps into the body. For smartwatches such as the Samsung Galaxy Watch 4 or the Fitbit Aria 2 smart scale, the electrical current flows through the body and the response is measured by the sensor to determine the person’s body composition such as skeletal muscle mass or fat mass. For smart rings such as the Moodmetric smart ring, bioimpedance sensing technology is used to measure a person’s level of stress.

After conducting testing of bioimpedance on three cardiac CRT devices from manufacturers Medtronic, Boston Scientific and Abbott, the team learned the slight electrical currents from these wearable gadgets can interfere and sometimes confuse cardiac implantable devices into operating incorrectly.

In the case of a pacemaker, which sends small electrical impulses to the heart when it is beating too slowly, the bioimpedance’s tiny electrical current could trick the heart into thinking it is beating fast enough, preventing the pacemaker from doing its job when it is supposed to.