How do Fitbit Irregular Rhythm Notifications check for atrial fibrillation (AFib)?

Atrial fibrillation (AFib) is a type of irregular heart rhythm of the upper chambers of the heart (the atria). Normally, the upper chambers contract regularly to move blood into the lower chambers. With AFib, the upper chambers contract irregularly, causing some blood to move slowly in the upper chambers. This slow-moving blood can clot, which raises the risk for stroke and heart-related issues. Learn more from the CDC or the European Society of Cardiology.

Fitbit smartwatches and trackers have optical sensors that can detect the pulse of blood that goes to your wrist with every heartbeat. The Fitbit Irregular Rhythm Notifications feature collects heart rhythm and motion data to check for signs of AFib. When you turn on the feature, your heart rhythm data are collected in the background while you are still or sleeping, and analyzed for AFib when your data sync with the Fitbit app. After your consumer wrist-worn product collects enough analyzable pulse rate data, we look at your beat-to-beat measurements to check for irregularities. Beat-to-beat measurements indicate how quickly one heart beat comes after the other . It’s typically measured in milliseconds (ms) and converted into beats per minute (bpm). Normally, these measurements are relatively predictable and smooth. Big increases or decreases (over 10 bpm) in a short period of time may be considered irregular.

1. From the Discover tab in the Fitbit app on your phone, tap Assessments & Reports.
2. Tap the Irregular Rhythm Notifications tile.
3. Tap Set Up Now, and follow the on-screen instructions.

Fitbit can only capture your pulse rate data for AFib when you’re still. Wear your compatible watch or tracker often, especially to sleep, and sync your data to look for signs of AFib more often. For tips on how to wear your watch or tracker, see How do I wear my Fitbit device?

Irregular Rhythm Notifications are available on:

• Fitbit Charge 3 running firmware version 1.88.11 or higher
• Fitbit Charge 4 running firmware version 44.1.100.43 or higher
• Fitbit Charge 5 running firmware version 1.149.11 or higher
• Fitbit Inspire 2 running firmware version 44.1.124.34 or higher
• Fitbit Inspire 3 running firmware version 63.200001.179.13 or higher
• Fitbit Luxe running firmware version 1.151.16 or 1.146.4 or higher
• Fitbit Sense running firmware version 44.128.6.12 or higher
• Fitbit Sense 2 running firmware version 60.20001.169.126 or higher
• Fitbit Versa 2 running firmware version 35.72.1.9 or higher
• Fitbit Versa 3 running firmware version 36.128.6.12 or higher
• Fitbit Versa 4 running firmware version 61.20001.169.337 or higher
• Fitbit Versa Lite Edition running firmware version 38.72.1.9 or higher

If an incompatible device is paired after the user has consented to the feature, the algorithm will not analyze data from an incompatible device.

The Fitbit app requires iOS 14 or higher or Android 9 or higher. For additional information on device compatibility with the Fitbit app, see fitbit.com/global/us/technology/compatible-devices.

Note that the Fitbit Irregular Rhythm Notifications is only available in select locations at this time. Additional devices & countries will be added as regulatory clearance is obtained. See fitbit.com/irregular-rhythm for additional details.

Fitbit doesn’t analyze your data in real time. If you receive a notification, it means we saw signs of an irregular rhythm that may be AFib in the last 24 hours (with regular device syncing).

Phone notification

If you allow notifications from the Fitbit app on your phone, you see a notification on your phone:

Tap the notification to open the Fitbit app.

Fitbit app notification

When you open the Fitbit app, you see a notification at the top of the Today tab:

Tap View Now to see the readings where we saw signs of an irregular heart rhythm, or tap the X icon to dismiss the notification.

If you receive an irregular rhythm notification, you should talk to your doctor.

1. From the Discover tab in the Fitbit app on your phone, tap Assessments & Reports.
2. Tap the Irregular Rhythm Notifications tile. If Fitbit detects signs of any irregular heart rhythms that might be AFib, you see a list of notifications and when they occurred. Note that each notification is marked Unread until you tap it to view more information.
   
   
3. Tap a notification for detailed information. A list of irregular rhythm readings appears, marked with the time when the reading occurred, and the minimum and maximum heart rate during that time period. Swipe up to see the summary at the bottom of the page, which lists the date and time of the first irregular rhythm reading, last irregular rhythm reading, and when the data was recorded in the Fitbit app.
4. Tap an irregular rhythm reading for additional information. A list of your beat-to-beat measurements appears. Each heartbeat has a bpm value and a timestamp of when it occurred. The summary at the top displays the minimum and maximum bpm value recorded.

1. From the Discover tab in the Fitbit app on your phone, tap Assessments & Reports.
2. Tap the Irregular rhythm notifications tile.
3. Tap the notification you want to delete.
4. Swipe up and tap Delete notification at the bottom of the page Yes, delete notification.

Fitbit doesn’t analyze your data in real-time. Keep the Fitbit app running in the background to make sure your compatible watch or tracker can regularly sync. To check when your heart rhythm data was last analyzed:

1. From the Discover tab in the Fitbit app on your phone, tap Assessments & Reports.
2. Tap the Irregular rhythm notifications tile. The time and date when your data was last analyzed appears below your history of notifications.

If your data hasn’t been analyzed in several days, follow the troubleshooting steps in Why won't my Fitbit device sync?

Note that data is stored on your watch or tracker for 7 days. If you haven’t synced with the Fitbit app in over 7 days, older data might be deleted and won’t be analyzed.

If your phone doesn’t receive push notifications from the Fitbit app:

• Turn on notifications for the Fitbit app in your phone's settings. For instructions, see support.google.com for Android phones or support.apple.com for iPhones.
• Check that the Fitbit app on your phone is updated. For instructions, see How do I use the Fitbit app?

Fitbit can only analyze your heart rhythm data for AFib when you’re still. Wear your consumer wrist-worn product often, especially to sleep, and sync your data often to help look for signs of AFib more often. We only send a notification if we see signs of an irregular rhythm in multiple readings, which means you might not receive irregular rhythm notifications if we’re not able to collect enough data each day.

To troubleshoot heart-rate tracking, see What factors can affect my heart-rate reading on my Fitbit device?

A clinical study was performed to validate the Fitbit Irregular Rhythm Notifications (IRN) software algorithm’s ability to detect atrial fibrillation (AFib) using data collected from consumer wrist-worn products. The Fitbit Validation of Software for Assessment of Atrial Fibrillation From PPG Data Acquired by a Wearable Smartwatch Study (NCT04380415) included 455,699 subjects. There were 4,728 subjects who received an irregular rhythm notification and were invited to receive and wear an electrocardiogram (ECG) patch. Of those, 1,057 wore and returned a 7-day ECG patch monitor with usable data. The prevalence of AFib based on the 7-day ECG patch monitoring results was 32.2% (340/1057).

The Fitbit Irregular Rhythm Notifications software algorithm detected signs of AFib in 225 subjects while they were wearing an ECG patch after an initial IRN notification. Of those, 98.2% (221/225) showed AFib detections from the Fitbit Irregular Rhythm Notifications software algorithm and the ECG patch at approximately the same time. No serious adverse events were observed during the clinical study.

Fitbit Irregular Rhythm Notifications collects pulse rate data in the background when you’re still or at rest by analyzing beat-to-beat measurements. It uses the optical pulse-rate sensor on your compatible wrist-worn product to identify heart rhythm changes. If multiple readings show an irregular pulse rate that may be AFib, you receive a notification. Data isn’t analyzed in real-time.

The Fitbit ECG app uses electrical sensors on the back of your compatible Fitbit product and on the metal frame around its face to allow you to record the electrical signals from your heartbeat during a 30-second reading. The Fitbit ECG app is qualitatively similar to a Lead I ECG in that it can be used to discriminate between AFib and normal sinus rhythm. The Fitbit ECG app analyzes the recording and presents the results on your watch or tracker. For more information, see What is the Fitbit ECG app?

No. Fitbit Irregular Rhythm Notifications isn’t intended for use in individuals previously diagnosed with AFib.

You might not receive a notification for every episode of irregular rhythm suggestive of AFib if sufficient data isn’t available. The absence of a notification doesn’t mean you don’t have AFib. For this reason, the feature shouldn’t be used as a monitoring tool. Please talk to your doctor if you’re looking to monitor your previously diagnosed AFib.

DO NOT change your medication without first speaking to your doctor. The results of the Fitbit Irregular Rhythm Notifications may not be accurate in people who take medication or substances that affect heart rate or heart rhythm.

DO NOT use this product in place of treatment prescribed by your doctor. Palpitations and shortness of breath can be symptoms of AFib, but some people don’t have any symptoms. AFib is treatable, so the earlier you detect it, the sooner you and your doctor can do something about it. If you receive a notification and have not been diagnosed with AFib by a physician, you should talk to your doctor. Erroneous false negative or false positive results due to the device or user error may occur. If you don’t get a notification, it’s possible to still have AFib. Fitbit is not always looking for AFib. We can’t notify you for all instances of irregular heart rhythm that may be AFib. For more information on the performance of Fitbit Irregular Rhythm Notifications, see How accurate are irregular rhythm notifications?

No. Fitbit Irregular Rhythm Notifications has not been tested for and is not intended for use in people under 22 years of age.