A randomized Dutch trial has given fresh, hard numbers to a claim many clinicians and patients have suspected for years: consumer smartwatches can pick up atrial fibrillation that conventional care misses.
In the EQUAL study, researchers at Amsterdam UMC enrolled 437 outpatients aged 65 and older with an elevated stroke risk and randomized them to six months of either usual cardiology care or continuous monitoring with an Apple Watch equipped with photoplethysmography (PPG) and single‑lead ECG functionality. The result was stark: 9.6% of patients wearing the watches were diagnosed with AF within 180 days versus 2.3% of those receiving standard care — roughly four times as many diagnoses (hazard ratio 4.40, 95% CI 1.66–11.66).
Why that matters
Atrial fibrillation is often brief and symptomless, yet it raises stroke risk substantially. Identifying AF in people whose CHA2DS2‑VASc scores make them candidates for anticoagulation can change treatment and, potentially, outcomes. In EQUAL more than half of the smartwatch‑detected AF episodes (about 57%) were asymptomatic—cases that probably would never have prompted an ECG under normal care.
Numbers that tell a practical story
- Participants: 437 (median age 75; 46.7% women; median CHA2DS2‑VASc = 3)
- Monitoring target: Apple Watch worn ≥12 hours/day while awake; 30‑second ECG recordings prompted by symptoms or an irregular‑pulse notification
- Diagnoses at 6 months: 21 in the smartwatch arm vs 5 in controls
- Absolute increase: 7.3% → number needed to screen ≈ 14
- Algorithm performance: of 37 watch‑flagged patients, 20 were ultimately adjudicated as clinical AF (positive predictive value ≈ 54%)
- For people over 65 with stroke risk factors, wearable monitoring can substantially increase AF detection compared with standard intermittent testing.
- Device alerts should not be treated as final diagnoses; clinical confirmation (an adjudicated ECG and specialist input) is critical before starting long‑term anticoagulation.
- Health systems planning to use consumer wearables need telemonitoring workflows and clear follow‑up protocols to avoid unnecessary anxiety and downstream testing.
How the workflow worked
The study embedded the consumer devices into a clinical telemonitoring pathway: ECGs recorded on the watch were sent to a telemonitoring service (HartWacht) and reviewed by trained cardiac nurses and supervising cardiologists within 24 hours. That clinical adjudication step matters — it reduced the risk of acting on false positives. All patients with confirmed AF were started on oral anticoagulation according to treating cardiologists' decisions.
Benefits, caveats and unanswered questions
The trial demonstrates feasibility and a diagnostic advantage, but it did not prove that earlier detection translated into fewer strokes, less heart failure, or improved survival. EQUAL wasn’t powered to detect those clinical outcomes; event rates (ED visits, major adverse cardiovascular events) were numerically similar between groups over six months. Open‑label design and the absence of a sham device are additional limitations that can influence health‑seeking behavior.
There’s also a human cost-benefit balance to consider: false positives can cause anxiety and trigger extra testing; yet missed AF can mean missed opportunities to prevent stroke. The study’s design — combining continuous consumer monitoring with rapid clinical adjudication — is a pragmatic attempt to thread that needle.
What cardiologists are saying
Lead investigators argue that smartwatches could offer a scalable bridge between broad digital detection and evidence‑based treatment. Michiel Winter, a cardiologist involved in the trial, suggested the diagnostic gains and possible stroke‑risk reductions might offset the upfront device cost. Others point out that large outcome trials (such as REGAL and SAFER, and the much larger Heartline program) are needed to show whether screen‑detected, often subclinical AF should be managed the same way as symptom‑driven diagnoses.
Implementation matters
EQUAL’s model—consumer device + telemonitoring + clinician adjudication—provides a template for real‑world use. It also highlights system needs: clear pathways for follow‑up, capacity for remote ECG review, and reimbursement models that cover device and monitoring costs. As Apple and other platforms continue to evolve how watches and iPhones interact, clinicians and health systems will have to decide how to integrate alerts into routine care; Apple itself is making changes to Watch–iPhone behavior in regions such as the EU as the platform adapts to new rules and features (/news/apple-eu-wifi-sync-removed). Apple’s broader software updates — the company still tweaks iOS and Watch integration across services — are part of that ecosystem shift, for better or worse (/news/apple-podcasts-auto-chapters-links).
Practical takeaways for patients and clinicians
If you’re shopping for a device or curious about trial results: the study used Apple Watch models with PPG and ECG features. If you want to explore the hardware on the market, the Apple Watch used in many clinical workflows is widely available on retail channels.
EQUAL doesn’t close the chapter on smartwatch screening — it opens it. The study moves the conversation from anecdotes to randomized evidence that wearable‑based monitoring can find clinically actionable AF that otherwise goes unseen. Whether that detection will translate into better long‑term outcomes is the next, more consequential question; a question ongoing outcome trials are poised to answer.