Summary: A study funded by ŌURA and conducted by Brigham and Women’s Hospital compared the sleep-tracking accuracy of the Oura Ring, Apple Watch, and Fitbit Sense against gold-standard polysomnography. The study found that the Oura Ring outperformed the other two devices in four-stage sleep classification accuracy, wake detection, and deep sleep detection. While all three devices were effective at distinguishing sleep from wake, the Oura Ring demonstrated the highest overall accuracy and sensitivity.
Key Takeaways:
- Oura Ring Leads in Accuracy: The Oura Ring was found to be 5% more accurate than the Apple Watch and 10% more accurate than Fitbit in four-stage sleep classification compared to polysomnography.
- Superior Wake and Deep Sleep Detection: Oura Ring had the highest sensitivity for both wake detection (68.6%) and deep sleep detection (79.5%), outperforming both the Apple Watch and Fitbit in these metrics.
- No Significant Misestimations: Unlike the Apple Watch, which overestimated light and deep sleep, the Oura Ring did not significantly underestimate or overestimate any of the four sleep stages.
A study evaluating the accuracy of sleep-staging algorithms in three consumer wearable devices—Oura Ring, Fitbit Sense, and Apple Watch—against gold-standard polysomnography found that Oura Ring was the most accurate sleep tracker in four-stage sleep classification.
The 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. The study was published in Sensors and presented at Sleep Europe 2024.
“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,” says Rebecca Robbins, PhD, lead author of the study, sleep scientist at Brigham and Women’s Hospital, and medical advisor for ŌURA, in a release. “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.”
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 5% more accurate than Apple Watch and 10% 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% compared to 67.7% for Fitbit and 52.4% for Apple Watch.
- Oura Ring had the highest sensitivity for deep sleep detection at 79.5% compared to 61.7% for Fitbit and 50.5% 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.
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% of the night.
The results of the validation study revealed that “all the devices exhibited sensitivity of 95% or more for identifying sleep and more than 90% agreement in the determination of sleep vs wake (ie, a two-stage classification), surpassing many older research-grade actigraphy devices, which in many cases demonstrated 86–94% agreement with PSG in a two-stage classification,” the researchers write.
The researchers conclude, “Our analyses revealed that all three devices perform extremely well in distinguishing between sleep and wake.”
Photo caption: (L to R) Oura Ring, Apple Watch, Fitbit
File photos
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