In-depth: ​Fitbit’s continuous Afib tracking feature explained

We speak to Fitbit research scientist to get deep into Afib detection
​Fitbit’s continuous Afib tracking explained
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Back in April, Fitbit rolled out a major new health feature in the US, which has the power to save thousands of lives.

Its passive, continuous atrial fibrillation monitor feature takes the wearable tech fight against Afib up a gear.

Atrial fibrillation is an irregular heart rate condition, and the leading cause of strokes in the US. It’s estimated to affect 44 million people, and most don’t even know they have the condition.

It’s been a big focus of wearables in recent years, with the likes of Apple, Fitbit and Samsung adding ECG sensors to their smartwatches, which can detect the signs of Afib. But this relies on a user taking the reading at the right time.

Now Fitbit’s gone one further, and it can detect Afib without any input from the user via its FDA-approved feature. Whats more, because the technology uses the existing heart rate sensor, it's rolling the feature out across its wide range of trackers and smartwatches.

You can read about it further on the Google blog.

Why tracking Afib is important

fib in Fitbit app

“The prevalence of AFib has been growing steadily over the past few decades. This is becoming problem in both the developed world and also low and middle income countries, so we're trying to help as many people as we can,” Fitbit research scientist Tony Faranesh told Wareable in an interview.

“For many people Afib is paroxysmal or episodic – meaning it comes and goes. And they can also be asymptomatic. Having longer term monitoring is an important feature to detect it early.”

That means that taking an ECG might not show signs of Afib, even if you suffer from the condition.

"Fatigue, dizziness, being out of breath, heart racing are all symptoms of Afib," said Faranesh, so taking an ECG at that point is useful. But that doesn't work if you're asymptomatic. So background monitoring increases the chances of your device finding a problem.

How does Fitbit continuous Afib detection it work?

Rather than using an ECG sensor, the new passive monitoring uses the Fitbit PPG sensor, which usually tracks heart rate.

“We look at the past 24 hours, and we will notify users that we've seen or observed an irregular rhythm – and give them a timestamp,” said Faranesh. “We want to help people draw connections between potential triggers, but it's not meant to be real time."

If an irregular rhythm is detected, users will be notified via the Fitbit dashboard.

But it’s an opt-in feature, which means users will need to head to the Health Assessment menu and manually switch it on. There’s also an onboarding process and some inclusion criteria.

You need to reside in the US, aged 22 years and older, and that you don't have an existing diagnosis of Afib.

Which devices support continuous Afib?

Fitbit range continuous afib

Fitbit is rolling the feature out to its whole range, taking advantage of the PPG sensor in its devices. Users in the US can opt-in via:

  • Charge 5
  • Charge 4
  • Luxe
  • Sense
  • Versa 3
  • Versa 2
  • Inspire 2

PPG vs ECG

So is the method of scanning for Afib better via the PPG sensor better than the ECG we’ve seen on the likes of the Fitbit Sense or Apple Watch Series 7?

“It's really to give people to two different sets of tools,” said Faranesh.

“But the longer you look, the more you find, because disease can present itself and they go away and present itself,” he said.

“I think having this background monitoring is an important part of the toolbox in terms of helping people figure out if they have a condition as early as possible, and get them appropriate care.”

What if Afib is detected?

Fitbit’s continuous Afib tracking explained

So what happens if a user gets flagged for an Afib event?

‘We provide users with a number of with information about the disease itself about atrial fibrillation about why it's important to follow up, namely, there's a risk factor for stroke.

“So even if you don't feel symptoms, you should follow up with a health care provider because your provider can sort of take the sort of holistic view about your health, the risk of you having a condition and offer a confirmatory test.”

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