Apple Watch AFib Detection Has Its Limitations, Study Shows

Apple's success in the smartwatch segment is something everyone is familiar with. The Apple Watch, however, has not only been a success in the smartwatch segment, but also the health tech sector, with the ECG feature on its Series 4 and Series 5 watches, that has claimed to have saved several by detecting atrial fibrillation (AFib) – a condition associated with abnormal heart rate, making a person prone to strokes. A recent study shows however that the sensitive

Now, according to a 2019 study published in the New England Journal of Medicine (NEJM), which examined 420,000 cases over a course of eight months, concludes that the Apple Watch was effective in detecting AFib consistently in 84 percent cases. The study, funded by Apple itself, determined that the Apple Watch was effective in determining arrhythmia.

However, the study does not mention that the Apple Watch can not detect a heart rate of more than 120 beats per minute (BPM), notes an opinion piece by John Nosta, founder of NostaLab, in Fortune. Apple however mentions it in a filing with the US FDA to get the feature approved. To be clear, Apple doesn't claim to diagnose AFib, and its detections or notifications are then meant to be corroborated by a physician's diagnosis. "Apple Watch is not constantly looking for AFib. This means Apple Watch cannot detect all instances of AFib, and people with AFib may not get a notification," its support page adds.

Coming to the most recent study, published earlier this week in Circulation, researchers found that the ability of the Apple Watch to detect AFib in a group of post-cardiac surgery patients was not as accurate. It found out that the Apple Watch detected the abnormality in only 34 of the 90 instances, a sensitivity of 41 percent.

Hence, the Apple Watch has not been as accurate in terms of detecting an irregular heart rate in post-cardiac surgery patients, who commonly experience AFib. Also, if the heart rate goes beyond the 120bpm limit, the Apple Watch will not be able to detect it. A 2015 study cited by the Fortune piece notes that roughly one-third of patients in a 2,821-patient study had a heart rate of above 120bpm when experiencing AFib, though the mean was 109bpm.

Apple had first launched the ECG feature in its Apple Watch Series 4 in 2018, carrying over the feature to the Apple Watch Series 5 in 2019. The company has claimed that the Apple Watch has saved many lives across the world with help of the ECG feature, by alerting the user if they have an irregular heart rate.

The popularity of the Apple Watch is quite evident, with a recent Strategy Analytics report claiming that in 2019, the 31 million Apple Watch units shipped in 20198 outsold the entire Swiss watch industry.