Fitbit tests if smartwatch could measure blood pressure

This article has been updated with additional information about how the study will be structured.

As more devices offer wrist-based ECG measurements, many device-makers are setting their sights on wrist-based blood pressure readings. But there’s a long ways to go, as most wrist-based measurements have failed to prove as accurate as traditional blood pressure cuffs.

Fitbit is still giving it a try, by launching a study to see if its newest smartwatch can measure blood pressure using pulse arrival time (PAT), which measures how long it takes for blood to reach a person’s wrist after their heart beats.

The company said it found a correlation between PAT and blood pressure in a small, three-week study. Other studies show mixed results as to whether PAT could be clinically meaningful measurement for blood pressure.

One of the benefits of at-home blood pressure monitoring is that it can be easier to track changes over time and get more accurate measurements, especially for people who might be a little bit anxious about going to the doctor’s office.

In a blog post, Fitbit admitted that while there has been great interest in non-cuff blood pressure measurements, “… it has been rather elusive to date.”

“If high blood pressure was easier to measure, people could manage it earlier, which might help avoid preventable deaths from heart disease and stroke,” Fitbit Principal Scientist Shelten Yuen said in a statement.  “It’s a hard scientific challenge, and a lot of work remains to be done to understand the best way to do this, but we have a history of advancing technology to make previously inaccessible health metrics available to Fitbit users from their wrist, so it’s a challenge we’re very passionate about solving.”

The study will be open to people ages 20 and up who have a Fitbit sense smartwatch. Fitbit plans to enroll 5,000 users to start, and the study will run for a few months, depending on how many are able to participate.

Other wearable-makers are also pushing to offer blood pressure measurements as a feature. Samsung’s latest smartwatch uses an optical heart rate sensor for blood pressure monitoring, but users have to calibrate it using a traditional blood pressure measurement, since this method only measures changes in blood volume. The feature still hasn’t been cleared for use in the U.S.

Another smartwatch-maker, Omron, got FDA clearance in 2018 to use an inflatable wrist cuff to measure blood pressure.

But so far, research has pointed to challenges in getting accurate wrist-based measurements. For example, a 721-person study published in Hypertension found that wrist-based devices tended to give a higher reading than arm-based blood pressure devices. A likely explanation is that users might not have had their wrist in the correct position, at heart level.

Photo credit: Fitbit

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