Smartwatches detect AFib with high diagnostic accuracy

Recent research shows that smartwatches have "excellent" diagnostic accuracy when it comes to detecting atrial fibrillation. 

The research, published in JACC: Advances, aimed to provide a comprehensive assessment of the effectiveness of smartwatches in detecting atrial fibrillation (AFib) and to compare the diagnostic performance of the underlying technology in smartwatches for AFib detection. AFib, an irregular heart rhythm, affects nearly 5% of the U.S. population, or approximately 10.5 million adults, according to data from the University of California, San Francisco in 2024. It can lead to blood clots, stroke, heart failure and other cardiac complications.

Increasingly, smartwatches include FDA-cleared electrocardiogram (ECG) and photoplethysmography (PPG) features that can notify users if they have AFib. The Apple Watch was the first to obtain FDA approval for its single-lead ECG sensor in 2018, paving the way for Withings, Samsung, Fitbit and others.

However, the study authors noted that the efficacy of smartwatches for AF detection varies, making it essential to evaluate their diagnostic accuracy.

Thus, they conducted a systematic literature review across ScienceDirect, PubMed and CENTRAL for research published through January 2025. They assessed 90 studies for study eligibility and included 26 in the review. The studies collectively analyzed data from 17,379 patients with an overall AFib prevalence rate of approximately 11%. 

Researchers found that smartwatches had a pooled sensitivity of 94.81% for detecting AFib. A subgroup analysis revealed that sensitivity varied by the type of smartwatch. The Samsung smartwatch had the highest sensitivity at 96.59%. The Apple Watch trailed at 93.62%, and Withings and FitBit had sensitivities of 88.58% and 65.57%, respectively.

They also found that smartwatches had a pooled specificity of 96.12% for detecting AFib. The subgroup analysis showed that specificity also varied by device type. The Apple Watch had a specificity of 96.97%, with Samsung and Withings following closely behind with specificities of 95.81% and 95.03%, respectively. Meanwhile, Fitbit had a specificity of 79.29%. 

Further, the study compared two underlying technologies of smartwatch AFib detection features: PPG and ECG. The results show that PPG-based smartwatches have similar diagnostic accuracy to ECG-based smartwatches.

Still, researchers cautioned that study sample sizes could have significantly contributed to diagnostic performance, with larger studies reporting higher accuracy. 

"Further research is necessary to evaluate the efficacy of smartwatches in real-world, low-prevalence settings, where predictive value may vary," they concluded.

Diagnostic accuracy is not the only factor to consider when assessing smartwatches for AFib detection.

Prior research points to other potential negative impacts that users of smartwatches should be aware of. The study included 172 AFib patients receiving treatment at an outpatient electrophysiology clinic in North Carolina between Dec. 1, 2022, and Feb. 27, 2023. Of the 172 patients, 83 used a wearable device. 

The study shows that wearable device users reported higher rates of symptom monitoring and preoccupation with their symptoms compared with non-users. For instance, about 45% of users reported checking their heart rate or performing an ECG daily. Further, approximately 15% of wearable device users said they felt anxious, scared, or concerned in response to wearable alerts for high and low heart rates.

Anuja Vaidya has covered the healthcare industry since 2012. She currently covers the virtual healthcare landscape, including telehealth, remote patient monitoring and digital therapeutics.