Summary
Head-to-head comparison of five wearables against ECG gold standard during 536 nights of sleep. Oura Gen 4 achieved 99% concordance with ECG for HRV, significantly outperforming Whoop, Garmin, and Polar devices.
Methods
13 healthy adults, simultaneous ECG reference and multiple wearables during sleep, 536 total nights
Key Findings
- Oura Gen 4: 99% concordance (CCC), 6% mean error for HRV
- Oura Gen 3: 97% concordance, 7% mean error
- Whoop 4.0: 94% concordance, 8% mean error
- Garmin Fenix 6: 87% concordance, 10.5% mean error
- Polar Grit X Pro: 82% concordance, 16% mean error
Limitations
Small sample size, only nocturnal measurements, Oura accuracy decreased at HRV above 60ms
What This Means for You
For HRV accuracy, Oura Ring leads the pack, followed by Whoop. Garmin and Polar showed poorer agreement with ECG. If absolute HRV accuracy matters to you, ring-based measurement during sleep appears most reliable.
Source
Read the original paper in Physiological Reports ↗
Added to HRV Zone: 2025-01-07