Fitbit launches large-scale consumer health study to detect a-fib via heart rate sensors, algorithm

The effort is looking to enroll 200,000 to 250,000 device owners, and will support clinical evaluation and regulatory submissions of the company's PPG atrial fibrillation algorithm.
By Dave Muoio
12:45 pm

Fitbit announced this morning the launch of a new atrial fibrillation research study aiming to enroll hundreds of thousands of fitness-tracker and smartwatch owners.

Called the Fitbit Heart Study, it will passively and continuously monitor wearers' heart rates using the devices' photoplethysmography (PPG) sensors. A proprietary algorithm will interpret these readings and flag potential irregularities for follow-up: a free telehealth visit with a live doctor and, if needed, an ECG patch delivered through the mail to confirm the irregularity.

"The main goals are to see how well this model of healthcare – passive monitoring, virtual visits, comparing with a clinical diagnostic test – works for screening for atrial fibrillation," Tony Faranesh, a research scientist at Fitbit, told MobiHealthNews. "We're very excited for this study. We feel that our devices are really well suited for detecting a-fib, in that, because it's a disease that comes and goes, it's important that we have a long battery life ... and people don't have to take it off at night."

The Fitbit Heart Study is now recruiting U.S. adults aged 22 years or older who own any of Fitbit devices that support heart-rate tracking, a list that includes the Ionic, Inspire HR, Charge 3 and Charge 4 devices, as well as the full Versa family. The company says it will only share participants' data with study partners, and will immediately notify a user upon enrollment if a potential arrhythmia is detected within data logged up to 30 days prior to registration.

But seeing as most participants will likely never receive any of the system's arrhythmia notifications, Faranesh said that the company is hoping to enroll 200,000 to 250,000 of its device owners into the study so that its data analysis will satisfy regulators. Hitting these numbers will also help Fitbit better demonstrate that its approach won't yield too many false positives, added CTO and cofounder Eric Friedman.

"The regulatory community, while they want people who are sick to go to the hospital, they're also equally interested in [making sure] people who aren't sick don't go to the hospital," he told MobiHealthNews. "Because we're a consumer product, they want to make sure we have scope backing our proof that people won't overwhelm the medical system. That's part of the reason for the large size of this study."

And on the topic of Fitbit's regulatory efforts, the study announcement also came with a reaffirmation of the company's ongoing development of an on-board ECG feature for its devices. Friedman said that the company has wrapped up a pivotal trial and submitted the feature for approval from regulators, and stressed that ECG spot detection of atrial fibrillation and the Fitbit Heart Study's continuous PPG "guardian angel" approach are complementary efforts for round-the-clock health monitoring.

"ECG has a role, and we're working on ECG as well," he said. "But because we have a 24-hour product, we have the unique ability to understand what is happening in the human body holistically throughout the day.

"You can almost think of these working in parallel, where if you have an event and you're awake, we can alert you and say 'Hey, now might be a good time to take an ECG.' But that's not necessarily required, so these kind of work in tandem with each other instead of in opposition."


Fitbit has clearly made its mark in fitness and general health over the years, which allows the company to establish an increasing presence among employer and insurer wellness plans. And while the company's devices have also played a role in some clinical studies as a continuous-activity or sleep-health monitor, the launch of Fitbit's first large-scale study to identify a cardiac disease is a major step toward broader clinical use.

"We've leveraged heart rate from just saying 'Hey, this is kind of cool. You can see your heart rate through the day,' to things like understanding sleep stages, understanding when your heart rate is elevated. And recently we released something called Active Zone Minutes, which uses your heart rate to figure out an appropriate-level workout for you," Friedman said. "We're really excited about moving on to this heart health stuff. It's really thinking about 'How do we be proactive in terms of helping people identify their condition?'"

The results of the Fitbit Heart Study will help the company's ongoing regulatory efforts, but will also serve as another test of whether a consumer-device-driven detection and virtual-care model is viable at scale – a particularly relevant subject considering the industry's recent swing toward telehealth.

"We considered very carefully whether the timing was right to launch this trial amidst the COVID-19 crisis," Faranesh said. "Atrial fibrillation is still an important problem. It's not going away, and the design of the trial is that people can enroll, onboard and just participate virtually. It doesn't require people to have any additional contact with people. ... We're not introducing any risk, and people are relying on telehealth even more during these times. It's a good test of this healthcare model going forward."


It's hard not to draw comparisons between Fitbit's latest effort and those of Apple, its chief competitor in the smartwatch space.

The latter company launched its Apple Heart Study in conjunction with Stanford Medicine back in 2017, and eventually recruited more than 400,000 participants to the research project, which also relied on a heart-rate sensor and accompanying algorithm to detect potential arrhythmia. Since then, Apple has announced a small handful of Watch-based studies focused on sound exposure, menstrual cycles, heart rate and physical activity.

Apple also made atrial fibrillation detection a focal point for consumer wearables since introducing on-board ECG to its Series 4 device in late 2018, with others like Withings following suit in the years to come. And while Fitbit does not directly offer the functionality on its devices, third-party app-makers like FibriCheck have developed their own FDA-cleared apps and algorithms for PPG-based arrhythmia detection for Fitbits and other smartwatches.

Still, it's not like Fitbit has slowed much in the roughly half-year since signing the sale to Google. November came with an OS update sporting heart-rate and sleep-tracking features, while January saw the activation of blood-oxygen-level variability measurements for Sp02-enabled devices. The tail end of March also bore news of a new fitness tracker supporting GPS and heart-activity tracking.


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