Study record · validation · 2020

Feasible assessment of recovery and cardiovascular health: accuracy of nocturnal HR and HRV assessed via ring PPG in comparison to medical grade ECG

Kinnunen H, Rantanen A, Kenttä T, and Koskimäki H

Physiological Measurement, 41(4), 04NT01 · 2020

Why this study matters to CircaTest

Establishes Oura ring PPG validity for nocturnal heart rate and HRV against medical ECG: nightly average HR agreement r² = 0.996 (mean bias -0.63 bpm), nightly average HRV agreement r² = 0.980 (mean bias -1.2 ms), in 49 adults aged 15-72. CircaTest cites this study to support claims about ring-form-factor PPG signal quality during sleep. Important honesty caveat: this study does NOT directly compare wrist-vs-finger PPG placement; the CircaTest article body claim that this paper documented a placement advantage is overstated and was softened during the retrofit. The paper establishes ring PPG accuracy against ECG, which is the underlying point but not the placement comparison the article body originally implied.

Abstract

OBJECTIVE: To validate the accuracy of the Oura ring in the quantification of resting heart rate (HR) and heart rate variability (HRV). BACKGROUND: Wearable devices have become comfortable, lightweight, and technologically advanced for assessing health behavior.…

Read the full abstract on the source →

Source: PUBMED · Excerpt for fair-use commentary; full abstract via the source link

Population

Sample size

n = 49

Age

15-72 years

Reference standard

ecg

49 adults across a wide age range and physical activity status, simultaneous Oura ring PPG and gold-standard ECG measurement during sleep.

Devices and metrics

Oura ring (research configuration, predecessor of Gen 3 commercial release)

All studies for this device →

Metric	Value	95% CI	Note
Accuracy	see source	—	The abstract reports nightly average HR agreement with ECG as r² = 0.996 (not a percent accuracy figure). r² is correlation squared, not a sleep-stage agreement metric. CircaTest does not coerce r² into the 0-100% accuracy display; consult the source for the reported correlation value.
Accuracy	see source	—	The abstract reports nightly average HRV agreement with ECG as r² = 0.980. Same caveat as the HR row above.

Cite this study

Kinnunen H, Rantanen A, Kenttä T, and Koskimäki H (2020). Feasible assessment of recovery and cardiovascular health: accuracy of nocturnal HR and HRV assessed via ring PPG in comparison to medical grade ECG. Physiological Measurement, 41(4), 04NT01. https://doi.org/10.1088/1361-6579/ab840a

AI-assembled record · errors are possible

This page was built and is maintained by AI working from the published abstract and PubMed metadata for the cited study. CircaTest does not have access to the full text of every paper in its corpus. Categories of error that have happened on this site and could happen again include:

Per-device metric values inferred when the abstract reports only an aggregate range
Stage-specific accuracy figures pulled from secondary sources rather than the primary paper
Sample size or population characteristics missing from the abstract
Editorial framing in the curatorial note that overstates the study's actual scope
Year typos and author-name transliteration errors

Where a metric value reads see source, the published abstract did not contain that value and CircaTest deliberately left it null rather than guess. For any decision that depends on the underlying numbers, please consult the linked PubMed, PMC, or DOI source directly. Corrections are welcome via the about page.

Source links

Added to the CircaTest meta-analysis on 2026-04-06. How CircaTest evaluates studies →