ŌURA, maker of Oura Ring, the most trusted smart ring, today announced the results of a new sleep accuracy study published in the peer-reviewed publication, Sensors, and presented at Sleep Europe 2024, Europe’s leading congress on sleep medicine and sleep research. The study, conducted by researchers at Brigham and Women’s Hospital, evaluated the accuracy of sleep-staging algorithms in three consumer wearable devices—Oura Ring, Fitbit Sense, and Apple Watch—against gold-standard polysomnography and found that Oura Ring was the most accurate sleep tracker in four-stage sleep classification.

“While polysomnography remains the gold standard of sleep assessment, wearable technology offers promise for measuring sleep continuously, less intrusively, and more naturally, making it a more scalable solution for sleep measurement,” said Dr. Rebecca Robbins, lead author of the study at Brigham and Women’s Hospital, assistant professor of medicine, and medical advisor for ŌURA. “For those looking to use consumer sleep trackers to identify patterns and address sleep issues, reliability and accuracy are paramount when navigating the variety of offerings available.”  

By leveraging advanced machine learning techniques and one of the largest wearable sleep datasets collected to date, ŌURA research scientists developed a new sleep staging algorithm that was found to achieve 79 percent agreement with polysomnography in four-stage sleep classification. Research shows that polysomnography, which relies on human coders to score the night of sleep after data collection, achieves 83 percent sleep stage agreement, meaning that two technicians scoring the same night on separate occasions may only agree for about 83 percent of the night.

“Scientific validation and accuracy are at the core of everything we do at ŌURA, and the results of this new study are a testament to our team’s dedication over the last decade to advancing our tracking capabilities,” said Shyamal Patel, senior vice president of science at ŌURA. “The investments we have made in developing our sleep-staging algorithm allow us to provide an accessible and accurate way for our community, including consumers, clinicians, and researchers, to better understand sleep.”  

To evaluate the accuracy of the three devices, 35 participants were recruited for a single-night in-patient study. During the study, they were monitored with polysomnography while also wearing an Oura Ring, Apple Watch, and Fitbit Sense. 

Key findings include:

  • Oura Ring was five percent more accurate than Apple Watch and 10 percent more accurate than Fitbit in four-stage sleep classification, adjusted for chance and compared to gold standard assessments, based on Cohen’s kappa (Oura Ring: 0.65, Apple Watch: 0.60, Fitbit: 0.55).
  • Oura Ring had the highest sensitivity for wake detection at 68.6 percent compared to 67.7 percent for Fitbit and 52.4 percent for Apple Watch. 
  • Oura Ring had the highest sensitivity for deep sleep detection at 79.5 percent compared to 61.7 percent for Fitbit and 50.5 percent for Apple Watch. 
  • Oura Ring did not significantly underestimate or overestimate any of the four sleep stages, while Apple Watch overestimated light sleep by an average of 45 minutes and deep sleep by an average of 43 minutes. 

“A core finding of this study is that, unlike the other devices, Oura Ring can more reliably estimate the amount of time spent in each of the different sleep stages,” said Raphael Vallat, sleep scientist and lead machine learning scientist at ŌURA. “Because each stage of sleep possesses unique health benefits, having an accurate picture of how much time you’re spending in each is critical for those looking to improve their overall well-being. This level of accuracy enables users to find meaningful associations between their day-to-day behaviors, their sleep patterns, and their health.”

The results from this latest study align with and build upon the findings of previous research examining the accuracy of ŌURA’s sleep staging algorithm, including independent studies conducted by the National University of Singapore and the University of Tokyo.

Forty percent of participants were ages 20-29; 37 percent were ages 30-39; and 23 percent were ages 40-50. A variety of races and ethnicities were represented, and the participants were healthy and did not have any known sleep disorders. Of note, despite the devices being charged, synced, and initialized prior to participants wearing the devices, Fitbit failed to record any data for two participants and Apple Watch failed to record data for six participants. 

This study was funded by ŌURA and independently designed and conducted by researchers at the Brigham and Women’s Hospital (BWH) and carried out in the BWH Center for Clinical Investigation.

Oura Ring is not a medical device and is not intended to diagnose, treat, cure, monitor, or prevent medical conditions/illnesses.