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Experts say people with pacemakers and other implanted devices should be careful about using fitness trackers on smartphones. 10’000 Hours/Getty Images
  • Researchers say there is a possibility that fitness trackers on smartphones can interfere with the workings of implanted devices such as pacemakers.
  • They note that the risk isn’t high, but people with implanted devices should be cautious.
  • Experts say the issue could become more prevalent in the future as the use of fitness trackers continues to increase.

The technology within our bodies may have a problem with the technology on our bodies.

A study published today in the journal Heart Rhythm says smartwatches and other fitness trackers may interfere with pacemakers and other implanted devices.

Wearable devices usually focused on monitoring aspects of our health such as heart rate, blood pressure, and other vital signs, have become popular.

However, researchers say that, despite the obvious benefits, certain fitness and wellness trackers could also pose serious risks for people with cardiac implantable electronic devices (CIEDs) such as pacemakers, implantable cardioverter defibrillators (ICDs), and cardiac resynchronization therapy (CRT) devices.

Researchers looked at the functioning of CRT devices from three leading manufacturers while applying electrical current used during bioimpedance sensing.

Bioimpedance sensing is a technology emitting a small, imperceptible current of electricity (measured in microamps) into the body.

The electrical current flows through the body, with sensors measuring the response to determine the person’s body composition (i.e., skeletal muscle mass or fat mass), level of stress, or vital signs, such as breathing rate.

“Bioimpedance sensing generated an electrical interference that exceeded Food and Drug Administration-accepted guidelines and interfered with proper CIED functioning,” said Benjamin Sanchez Terrones, an assistant professor in the Department of Electrical and Computer Engineering at the University of Utah and a lead investigator for the study, in a statement.

Sanchez Terrones emphasized that the results, determined through careful simulations and benchtop testing, don’t convey an immediate or clear risk to people who wear the trackers.

However, he said the different levels emitted could result in pacing interruptions or unnecessary shocks to the heart.

“Our findings call for future clinical studies examining patients with CIEDs and wearables,” Sanchez Terrones said.

The interaction between general electrical appliances and, more recently, smartphones, with CIEDs has been studied over the past few years.

Nearly all implantable cardiac devices already warn wearers about potential interference from a variety of electronics due to magnetic fields – for example, carrying a mobile phone in your breast pocket near a pacemaker.

The researchers said the rise of wearable health tech has grown rapidly in recent years, blurring the line between medical and consumer devices. Until this study, the researchers said objective evaluation for ensuring safety hasn’t kept pace with new gadgets.

“Our research is the first to study devices that employ bioimpedance-sensing technology as well as discover potential interference problems with CIEDs such as CRT devices,” Sanchez Terrones said. “We need to test across a broader cohort of devices and in patients with these devices. Collaborative investigation between researchers and industry would be helpful for keeping patients safe.”

Dr. John Higgins, a professor of cardiovascular medicine with McGovern Medical School at UTHealth Houston, told Healthline experts have wondered about possible conflicts between interior and exterior devices since 2007.

“Smartwatches, smart scales, smart rings, and other smart devices/wearables are known to often have small magnets inside them e.g. Neodymium-iron-boron (NdFeB) magnets, which are small in size but produce strong magnetic fields,” Higgins said. “Which can interfere with the function of permanent pacemakers (PPMs) and automatic implantable cardioverter defibrillators (AICD’S) due to electrical interference. Usually, the wearable has to be quite close (less than) two to three inches away to create major issues.”

Higgins said possible complications include implanted cardioverter-defibrillator activation (firing) or deactivation and permanent pacemaker mode switch (so the pacemaker may not function normally).

“I have had no cases myself, but [I’ve] heard of some issues with AICD/PPM malfunction,” Higgins noted. “The electrophysiology doctors (the ones that insert AICDs & PPMs) usually warn patients.”

Dr. Jim Liu, a cardiologist at The Ohio State University Wexner Medical Center, told Healthline he hasn’t experienced any cases of smartwatches or other wearable tech interfering with internal medical devices.

Nor has he heard of doctors discussing a potential problem.

“I don’t believe doctors currently warn patients about wearable devices and interference with CIEDs,” Liu said. “As the study mentions, previous studies did not show any problems with bioimpedance devices and CIEDs.”

Liu said it’s important to remember the study is based on a simulated model and electric circuit.

“It’s not known if these findings translate to an actual human body,” Liu said. “More research would be needed before knowing if this is actually a real concern.”

Nancy Mitchell is a registered nurse and a medical writer and has managed care units for people with cardiovascular disease.

She told Healthline that with people becoming more involved with their own healthcare – and the wearable devices becoming more powerful – she could see a time when there could be problems.

“According to the findings, both pacemakers and smart devices function by emitting electric charges,” Mitchell said. “Smartwatches could potentially exceed the FDA-approved threshold for these voltages which, in turn, could impair the performance of pacemaker implants. In some cases, the increased voltage could manifest as shocks to the patients. That alone could heighten their anxieties, especially if they’re unaware of the actual cause of those occasional zaps.”

Mitchell said the risk would likely vary, depending on the user.

“It is challenging to single out any one brand or device in particular,” Mitchell said. “The charges emitted depend heavily on the individual’s biometrics. So, one device may cause complications for certain patients and not anything significant for others.”

Higgins said he doesn’t recommend people with internal devices use external health monitors.

“We do not recommend the use of these devices with bioimpedance technology in this population (PPMs or AICDs) due to potential electrical interference,” she said. “Patients should be told of this risk and advised to keep their wristbands/other wearables/other devices at least 6 inches away from their cardiac devices, and they should not wear them to sleep.”

Higgins said the problem will likely need addressing at some point.

“Some alternative technology to a magnet/magnetic field in these wearables may need to be developed, or a stronger barrier/forcefield in the AICD/PPM shield to block this interference may need to be developed,” he said.