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Journal · Sleep

Your REM Sleep Is the Guardian of Your Heart. Research on 6,785 People Proves It.

Less REM and deep sleep means higher risk of atrial fibrillation. Nature Medicine 2024 study and how the Digital Twin monitors your heart while you sleep.

Updated October 2, 2026

A longitudinal study in Nature Medicine (2024) monitored 6,785 people for a median of 4.5 years using commercial wearables linked to electronic health records. Reduction in REM and deep sleep is inversely associated with onset of atrial fibrillation.

Bedroom of an Engadine chalet just before dawn: cold bluish light from the window, pale linen sheets, a smart ring and watch resting on the nightstand; no faces.

The heart's data hides in sleep

Every hour less of REM or deep sleep is a cardiovascular health marker. The All of Us Research Program study demonstrated this association is independent of other traditional risk factors, making sleep monitoring a first-line cardiological tool.

Macro detail of a wearable ring and a smartwatch recording sleep phases in low light; night-blue tones, soft reflections; no faces.

The numbers: a precise indicator

Each percentage increase in REM is associated with reduced incidence of atrial fibrillation (OR 0.86), atrial flutter (OR 0.78) and sinoatrial node dysfunction (OR 0.72).

Luminous chart of REM and deep-sleep phases projected on the dark wall of a premium clinical room; soft light, order; no faces.

A higher percentage of deep sleep is associated with reduced AF probability (OR 0.87) and lower major depressive disorder (OR 0.93).

Chalet window at dawn framing the snowy Engadine peaks seen from an unmade bed; cold natural light, stillness; no faces.

What this means for your Digital Twin

The Digital Twin monitors REM and deep sleep every night. If it detects a declining trend over 7+ consecutive days, it generates an alert the referring physician can evaluate — to intervene when the risk is still preventable.

Silent corridor of an Alpine clinic at dawn, warm materials (wood and stone) and soft light; a mood of clinical calm; no faces.

The advantage of longitudinal monitoring

Cardiovascular risk builds over months. The Digital Twin detects this trend over time, transforming daily data into a clinically relevant risk curve.

Bedroom of an Engadine chalet just before dawn: cold bluish light from the window, pale linen sheets, a smart ring and watch resting on the nightstand; no faces.

Brittain et al. — Nature Medicine, Vol. 30 (2024) — https://www.nature.com/articles/s41591-024-03155-8 · www.nature.com

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