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Currently submitted to: Journal of Medical Internet Research

Date Submitted: Jan 26, 2021
Open Peer Review Period: Jan 26, 2021 - Mar 26, 2021
(currently open for review)

Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.

Accuracy Assessment of Oura Ring Nocturnal Heart Rate and Heart Rate Variability in Comparison to Electrocardiography: A Comprehensive Analysis in Time and Frequency Domains

  • Rui Cao; 
  • Iman Azimi; 
  • Fatemeh Sarhaddi; 
  • Hannakaisa Niela-Vilen; 
  • Anna Axelin; 
  • Pasi Liljeberg; 
  • Amir M. Rahmani



Photoplethysmography (PPG) is a non-invasive and low-cost method to remotely and continuously track vital signs. The Oura ring is a compact PPG-based smart ring, which has recently drawn attention to be used in remote health monitoring and wellness applications. The ring is employed to acquire nocturnal heart rate (HR) and heart rate variability (HRV) parameters ubiquitously. However, these parameters are highly susceptible to motion artifacts and environmental noises. Therefore, the validity of the parameters should be assessed separately in everyday settings.


We evaluate the accuracy of HR and time-domain and frequency-domain HRV parameters collected by the Oura ring against a medical-grade chest electrocardiogram (ECG) monitor.


We conducted overnight home-based monitoring using an Oura ring and an ECG Shimmer device. The nocturnal HR and HRV of 35 healthy individuals were collected and assessed. We evaluated the parameters within two tests: i.e., values collected from five-minute recordings (i.e., short-term HRV analysis) and the average values per night sleep. A linear regression method, the Pearson correlation coefficient, and the Bland–Altman plot were also exploited to compare the measurements of two devices.


Our findings showed low mean biases of the HR and HRV parameters collected by the Oura ring in both the five-minute and average-per-night tests. In the five-minute test, the error variances of the parameters were nevertheless different. The parameters provided by the Oura ring dashboard (i.e., HR and RMSSD) showed relatively low error variance compared to the HRV parameters extracted from the IBI signals. The Pearson correlation coefficient tests (P < 0.0001) indicated that HR, RMSSD, AVNN, and pNN50 had high positive correlations with the baseline values, SDNN and HF had moderate positive correlations, and LF and LF/HF ratio had low positive correlations. The HR, RMSSD, AVNN, and pNN50 had narrow 95% confidence intervals; however, SDNN, LF, HF, and LF/HF had relatively wider 95% confidence intervals. In contrast, the average-per-night test showed that the HR, RMSSD, SDNN, AVNN, pNN50, LF, and HF had high positive relationships (P < 0.0001), and the LF/HF ratio has a moderate positive relationship (P < 0.0001). The average-per-night test also indicated considerably lower error variances than the 5-minute test for the parameters.


The Oura ring could accurately measure nocturnal HR and RMSSD in both the five-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 five-minute test. On the other hand, the LF and LF/HF of the ring had high error rates in both the tests.


Please cite as:

Cao R, Azimi I, Sarhaddi F, Niela-Vilen H, Axelin A, Liljeberg P, Rahmani AM

Accuracy Assessment of Oura Ring Nocturnal Heart Rate and Heart Rate Variability in Comparison to Electrocardiography: A Comprehensive Analysis in Time and Frequency Domains

JMIR Preprints. 26/01/2021:27487

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