The prevalence of atrial fibrillation (AF) rises significantly with age; in the United States, AF affects 5% of individuals >65 years of age and 10% >80 years of age.¹ Older adults carry the greatest risk of AF-related stroke, yet diagnosis is commonly delayed given both its paroxysmal nature (i.e., office electrocardiograms [ECGs] can have unremarkable findings) and its frequent lack of symptoms (≥25% of AF cases are considered asymptomatic).²

Over recent years, trials including the AHS (Apple Heart Study) and Fitbit Heart Study (Validation of Software for Assessment of Atrial Fibrillation From PPG Data Acquired by a Wearable Smartwatch) have validated photoplethysmography (PPG) and single-lead ECG for AF detection.^3,4 However, these studies exemplified two critical limitations of the early wearable literature. First, participants were predominantly younger, with a median age in the 40s. Second, these trials were primarily designed to assess the accuracy of AF detection. A key question therefore remains: Does wearable-enabled AF detection actually improve clinical outcomes? This question is especially relevant for older adults who have both the highest burden of AF and AF-related embolic stroke.

To answer the question of how AF screening impacts clinical management and outcomes in older adults, the results of several large trials have now been published. The STROKESTOP (Systematic ECG Screening for Atrial Fibrillation Among 75 Year Old Subjects in the Region of Stockholm and Halland, Sweden) study, with long-term outcomes reported in 2021, included individuals in Sweden 75-76 years of age and used intermittent single-lead handheld ECG screening.⁵ Compared with usual care, screening increased AF detection and oral anticoagulant (OAC) use, and was associated with reductions (albeit modest) in a composite endpoint that included ischemic stroke and all-cause death. Rates of major bleeding leading to hospitalization did not differ significantly between groups, supporting a net clinical benefit from screening. However, the estimated number needed to invite to screening to prevent a single composite endpoint was 91.

The ARTESIA (Apixaban for the Reduction of Thromboembolism in Patients With Device-Detected Subclinical Atrial Fibrillation) study also included a mostly older cohort (mean age 77 years) and studied the impact on thromboembolic risks with OAC initiation after AF detected from implantable devices. The study included patients with device-detected subclinical AF, defined as episodes lasting between 6 min and 24 hours identified through pacemakers or defibrillators.⁶ Participants were then randomly assigned to apixaban or aspirin and followed for a median of 3.5 years. Apixaban reduced the annualized rate of stroke or systemic embolism from 1.24% with aspirin to 0.78% (hazard ratio [HR], 0.63), corresponding to a 37% relative risk reduction and approximately 0.46 fewer events per 100 patient-years. This benefit, however, came at the cost of an increased risk of major bleeding: 1.71% per year with apixaban versus 0.94% with aspirin (HR, 1.8), or approximately 0.77 excess bleeds per 100 patient-years. These findings suggest that even relatively short AF episodes may carry clinical significance, but they also underscore the delicate balance clinicians must weigh between preventing stroke and avoiding bleeding in older adults.

In contrast, other studies have demonstrated no reduction in stroke despite substantially higher AF detection and OAC initiation rates with more intensive AF surveillance. The LOOP (Atrial Fibrillation Detected by Continuous ECG Monitoring Using Implantable Loop Recorder to Prevent Stroke in High-Risk Individuals) study tested a more intensive strategy, randomly assigning adults 70-90 years of age with stroke risk factors to implantable loop recorders (ILRs) or usual care.⁷ As expected, AF detection and OAC initiation were significantly higher in the device group. After a median of 5.4 years, AF was detected in 31.8% of the ILR group and in 12.2% of the usual-care group, and OAC initiation more than doubled (29% vs. 13%). Nevertheless, the rate of ischemic stroke or systemic embolism was 4.5% in the device group and 5.6% in the control group (HR, 0.8; p = 0.11), and major bleeding occurred in approximately 4% of patients in both groups, with no significant difference. These findings underscored that increased detection rates do not necessarily translate into clinical benefit.

Similarly, the GUARD-AF (Reducing Stroke by Screening for Undiagnosed Atrial Fibrillation in Elderly Individuals) trial was the largest US test of whether patch-based AF screening could improve outcomes.⁸ Nearly 12,000 adults ≥70 years of age were randomly assigned to 14-day patch ECG monitoring or usual care. AF was diagnosed in 5% of the screened group and in 3.3% of the control group, with OAC initiation also higher (4.2% vs. 2.8%). Yet, stroke hospitalizations were virtually identical (0.7% vs. 0.6%) and major bleeding hospitalizations were comparable (1% vs. 1.1%). Of note, interpretation of the GUARD-HF trial results is complicated by early termination due to the coronavirus disease 2019 pandemic and an overall low event rate.

Taken together, the current evidence demonstrates that, although digital technologies reliably increase AF detection and OAC initiation, they have not consistently improved clinical endpoints including stroke or death. The ARTESIA trial results highlight the trade-offs: Strokes can be prevented, but at the cost of substantially more bleeding events in a vulnerable older population. Even in the most favorable case—the STROKESTOP study data—the number needed to invite for screening to prevent one composite endpoint was 91, which raises questions about the population-level efficiency of such programs. A separate factor to consider is the cost-effectiveness of such programs: An analysis based on STROKESTOP study data suggested cost savings from screening given the potential to avoid adverse downstream stroke-related health consequences.⁹ A caveat to these assumptions is that they remain sensitive to long-term anticoagulation adherence. Further, quality-of-life considerations (e.g., the burden of taking daily medications, or patient anxiety about future events) are often nuanced and not always fully addressed by such analyses.

What then are the implications for clinical practice? One possibility is that the greatest benefit may not be in very old adults, for whom bleeding risk, frailty, and multimorbidity complicate anticoagulation decisions, but rather in a younger segment of older adults (e.g., 65-74 years of age). In this group, bleeding risk is lower, strokes can be more devastating in terms of disability-adjusted life years, and medical contact may be less frequent. Precision screening strategies targeting this window could potentially be more effective than broad, population-wide invitations at ≥75 years of age.

Looking ahead, several large-scale studies may help clarify whether digital AF screening can ultimately improve outcomes. The Heartline (A Study to Investigate if Early Atrial Fibrillation [AF] Diagnosis Reduces Risk of Events Like Stroke in the Real-World) is enrolling >26,000 adults ≥65 years of age in the United States to test whether wearable-enabled AF detection combined with structured engagement pathways can lead to earlier anticoagulation and reductions in stroke, bleeding, and health care utilization.¹⁰ These studies and others will help inform future policy decisions regarding nationwide AF screening programs and provide evidence on the actionable window for intervention in asymptomatic AF.

References

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2. Pamporis K, Karakasis P, Sagris M, et al. Prevalence of asymptomatic atrial fibrillation and risk factors associated with asymptomatic status: a systematic review and meta-analysis. Eur J Prev Cardiol. Published online March 7, 2025. doi:10.1093/eurjpc/zwaf138
3. Perez MV, Mahaffey KW, Hedlin H, et al. Large-scale assessment of a smartwatch to identify atrial fibrillation. N Engl J Med. 2019;381(20):1909-1917. doi:10.1056/NEJMoa1901183
4. Lubitz SA, Faranesh AZ, Selvaggi C, et al. Detection of atrial fibrillation in a large population using wearable devices: the Fitbit Heart Study. Circulation. 2022;146(19):1415-1424. doi:10.1161/CIRCULATIONAHA.122.060291
5. Svennberg E, Friberg L, Frykman V, Al-Khalili F, Engdahl J, Rosenqvist M. Clinical outcomes in systematic screening for atrial fibrillation (STROKESTOP): a multicentre, parallel group, unmasked, randomised controlled trial. Lancet. 2021;398(10310):1498-1506. doi:10.1016/S0140-6736(21)01637-8
6. Healey JS, Lopes RD, Granger CB, et al. Apixaban for stroke prevention in subclinical atrial fibrillation. N Engl J Med. 2024;390(2):107-117. doi:10.1056/NEJMoa2310234
7. Svendsen JH, Diederichsen SZ, Højberg S, et al. Implantable loop recorder detection of atrial fibrillation to prevent stroke (the LOOP study): a randomised controlled trial. Lancet. 2021;398(10310):1507-1516. doi:10.1016/S0140-6736(21)01698-6
8. Lopes RD, Atlas SJ, Go AS, et al. Effect of screening for undiagnosed atrial fibrillation on stroke prevention. J Am Coll Cardiol. 2024;84(21):2073-2084. doi:10.1016/j.jacc.2024.08.019
9. Lyth J, Svennberg E, Bernfort L, et al. Cost-effectiveness of population screening for atrial fibrillation: the STROKESTOP study. Eur Heart J. 2023;44(3):196-204. doi:10.1093/eurheartj/ehac547
10. Gibson CM, Steinhubl S, Lakkireddy D, et al. Does early detection of atrial fibrillation reduce the risk of thromboembolic events? Rationale and design of the Heartline study. Am Heart J. 2023;259:30-41. doi:10.1016/j.ahj.2023.01.004