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Newspapers have reported that recent research has found smartwatches and other wearable fitness trackers could disrupt pacemakers and ICDs, putting people at risk. But is this true? We go behind the headlines.
Published 1 March 2023
A recent study published in the journal Heart Rhythm has raised questions about whether it’s safe for people fitted with pacemakers and ICDs to use certain types of smart scales and wearable fitness trackers.
The researchers, from the University of Utah, used lab tests and computer simulations to study the possible effects of selected smartwatches, smart scales and smart rings on pacemakers and ICDs.
The results confirmed that there is a risk of these trackers disrupting pacemakers and ICDs, with interference levels going above the standard recognised by the US Food and Drug Administration (FDA). They also found that smartwatches caused more disruption than smart scales and smart rings.
Only wearable devices which use a specific technology called ‘bioimpedance sending’ were studied by the researchers. Bioimpedance involves sending small, painless electrical signals into the body, and reading the signals that come back. They can estimate things like body fat percentage, heart rate and stress levels, helping people to take responsibility for their health.
Until now, however, little research has been done on the safety of these fitness trackers in people using lifesaving cardiac devices such as pacemakers.
While we already know that smartphones can interfere with pacemakers and ICDs, this study is a step towards filling the gap in what we know about smartwatches and other devices that use bioimpedance technology.
The study authors conclude that people with implantable devices should avoid wearable fitness trackers that use bioimpedance technology, due to the potential for interference. Whether a particular wearable uses bioimpedance should be listed in the product leaflet under ‘manufacturing information’.
In the paper, they state that “these commercially available devices… have the theoretical potential to interfere [with ICDs and pacemakers], with undesirably disastrous consequences”.
They also outline possible effects. For example, the interference from wearable fitness trackers could stop a pacemaker from doing its main job – delivering electrical impulses which tell the heart to keep beating at the proper rate.
Another example they give is the possibility of fitness trackers causing an ICD to deliver an unnecessary electric shock to the heart. This shock, called ‘defibrillation’, is intended to restart the heart when it has stopped beating. If this happened when the person was conscious, it would likely be painful and distressing.
Prof James Leiper, an associate medical director at the British Heart Foundation, said: “As more people wear smartwatches and other devices with body-monitoring technology, it is important to understand any potential interference they may cause with lifesaving medical devices like ICDs and pacemakers.
“This study is a first step in this process. However, more research needs to be done in this area to understand any effects in patients.”
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Hundreds of millions of people without pacemakers and ICDs are using this wearable technology to improve their exercise habits, eating behaviours and motivation to lead a healthier lifestyle. For those people, this study doesn’t change anything.
On the other hand, if you have a cardiac device and you also use bioimpedance trackers, you might want to contact your pacing clinic for guidance on whether it’s safe to continue doing so.
In the meantime, it’s a good idea to be cautious – think about avoiding bioimpedance technologies and always follow the manufacturer’s instructions for your cardiac device. Most pacemaker and ICD manufacturers have guidance online about which consumer items can cause a problem for your device. However, they may not have been updated yet to reflect these study findings.
With all the benefits they offer, you may be drawn to fitness trackers as a way of taking more control of your health. If so, your healthcare team will be able to discuss other ways of setting and tracking your health goals. Remember that the research only looked at a selection of smartwatches, smart scales and smart rings which use bioimpedance – there are other wearables out there which don’t use this potentially concerning technology, and they could be just as helpful for improving your health.
While helpful for monitoring your own health, keep in mind that these are recreational, not medical, devices. They are not diagnostic tools and are not intended to replace medical advice.
This is, so far, one of the most comprehensive studies ever done on the level of interference caused by wearable fitness devices using bioimpedance technology.
It probably wouldn’t have been safe to do this kind of research on real humans, which led the researchers to use a computer simulation paired with testing the devices in a lab.
This doesn’t mean it was unreliable; one strength of using computers is the ability to create a consistent model of the human body. In comparison, there are many more factors to consider when it comes to a real group of people.
Another advantage of simulations is that the researchers could rule out other sources of interference, such as electromagnetic waves coming from nearby devices.
However, computerised models are only a rough approximation of the human body, and this does bring limitations. Given these limitations, the researchers have called for future clinical studies to examine this issue in more depth.
One further limitation is that the researchers tested the bioimpedance technologies on a specific type of ICD, called a CRT-D, on its most sensitive setting. The aim was to emulate a ‘worst-case scenario’, but this probably doesn’t reflect what would happen with the CRT-D on its typical setting.
This research was covered by several newspapers, including The Guardian, Sky News and The Sun.
The Guardian accurately reflected the tentative nature of the study’s findings, with the headline saying that wearable fitness trackers “could interfere” with cardiac devices. The article then presented a measured take on the findings, emphasising that they are more of a “red flag” than a precise indicator of risk. They also included a quote from Dr Benjamin Sanchez Terrones, one of the study authors, who commented that further research is needed to determine the actual level of risk.
The article by The Sun reported similarly, although in some places it made the findings sound more definite than they really were. For instance, it reported that smartwatches “can trick pacemakers into thinking the heart is beating correctly”. At this stage in the research, this isn’t something which has been proven beyond all doubt.
More worryingly, a dramatic headline by Sky News claimed that smartwatches “could trigger heart attacks” in “vulnerable” patients. This is misleading on two counts.
First, by not being clear that the study related to people who have ICDs or pacemakers, there is a risk of overgeneralising the conclusions and causing unnecessary concern in people who don’t have implantable cardiac devices.
Second, nowhere in the study did the authors mention a potential for smartwatches to trigger heart attacks. Pacemakers send electrical signals to the heart, telling it to beat in the right rhythm. If disrupted, the heart might start to beat irregularly, or in a worst-case scenario, to not beat at all. This is called cardiac arrest, and it is different to having a heart attack. The article doesn’t make this clear.
Watch our animation to understand the difference between heart attack and cardiac arrest
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