Does the Oura Ring accurately measure nocturnal heart rate and heart rate variability compared to electrocardiography?
The Oura Ring provides accurate nocturnal HR and RMSSD measurements but is unreliable for low-frequency HRV metrics compared to standard ECG.
The Oura Ring could accurately measure nocturnal HR and RMSSD in both the 5-minute and average-per-night tests. It provided acceptable nocturnal AVNN, pNN50, HF, and SDNN accuracy in the average-per-night test but not in the 5-minute test. In contrast, the LF and LF:HF ratio of the ring had high error rates in both tests.
Cao et al. (2021) studied this question.