Oura Smart Ring Faces US Class Action Over Alleged Misleading Sleep-Tracking Claims

It’s the kind of claim that sells a lot of smart rings. “95% sleep staging accuracy compared to a clinical sleep lab.” Bold, reassuring, and — according to a newly filed US lawsuit — potentially misleading.

A proposed class action complaint has been filed in the US District Court for the Northern District of California against Oura Inc. And related entities, including Oura Health Oy, the Finnish parent company behind the popular Oura Ring. The case, brought by Clarkson Law Firm on behalf of lead plaintiff Madison Surber, targets the Oura Ring 5, Oura Ring 4, and Oura Ring 4 Ceramic — the company’s current flagship wearables, which retail for around $300 (roughly £235) in the US.

The core allegation is blunt: that Oura rings cannot directly measure any of the physiological signals needed to assess sleep quality or determine sleep stages, and that the data they produce relies on AI-generated estimates described in the complaint as having “a coin flip’s chance of being correct.”

What the Lawsuit Actually Claims

Sleep stages — light, deep, and REM — are defined clinically by brain electrical activity (EEG), eye movements (EOG), muscle tone (EMG), and other parameters captured during polysomnography, a multi-sensor clinical test. Consumer wearables, including smart rings and watches, cannot directly measure brainwaves or eye movements. Oura rings instead track secondary signals: heart rate, heart rate variability, movement, breathing patterns, and skin temperature from the finger.

The complaint argues that using these secondary signals to infer sleep stages is not the same as measuring them — and that Oura’s marketing language, including the phrase “unparalleled accuracy,” crosses the line from reasonable approximation into consumer deception.

Madison Surber, the named plaintiff, says she bought an Oura ring in May 2025 on the strength of those accuracy claims, only to find — she alleges — that the device failed to accurately measure her sleep duration, number of awakenings, and overall sleep quality. She’s seeking to represent a wider class of consumers who made similar purchases based on the same marketing.

The Nature Study at the Centre of the Dispute

The lawsuit leans heavily on a 2025 study published in the journal Nature, which examined 45 nights of sleep across 45 Oura ring users. The findings were striking. Overall sleep-stage classification accuracy came in at around 53.18% — barely above chance. The rings reportedly overestimated REM sleep by about 31 minutes per night, underestimated light sleep by almost 14 minutes, and underestimated deep sleep by almost 6 minutes.

That sits a long way from the 95% accuracy figure Oura has used in marketing its Ring 5. Reports also suggest the company previously cited around 79% accuracy before updating its claims to 95%, though that earlier figure is drawn from media commentary rather than verified company filings.

The gap between 53% real-world performance and 95% advertised accuracy is, according to the plaintiffs, the heart of the problem.

Oura Pushes Back

Oura has not taken the claims lying down. The company disputes the lawsuit’s central argument, stating that its rings estimate sleep stages using multiple physiological signals — heart rate, heart rate variability, movement, breathing patterns, and temperature — and that well-documented, peer-reviewed evidence links those signals to sleep stages.

In short, Oura’s position is that its approach is scientifically grounded, even if the ring doesn’t attach electrodes to your scalp.

The company hasn’t issued a full public statement specifically addressing the Nature study’s 53% figure, but its broader defence is that correlation between measurable finger-worn signals and sleep stages is real and established. Whether that defence holds up in a California federal court is unclear.

A Wider Question for the Wearables Industry

This case doesn’t exist in isolation. It’s part of a growing pattern of legal and regulatory scrutiny around health-related claims made by consumer technology companies — covering everything from heart-rate monitoring and calorie counting to step tracking and, now, sleep staging.

Sleep researchers and clinicians have long been cautious about consumer wearables, generally treating them as useful for spotting broad trends rather than producing clinical-grade data. The Nature study, if its findings hold up to scrutiny, gives that caution a number to point to.

But plenty of consumers find real value in wearables for behaviour change and general awareness, even without clinical precision. The debate, then, is less about whether these devices are useful and more about whether the marketing accurately describes what they can and cannot do.

The outcome of this case could shape how wearable brands — not just Oura — communicate accuracy claims to consumers across the US, UK, and beyond.

What This Means for Kent Residents

If you own an Oura ring in Kent, it’s worth treating sleep-stage data as a rough guide rather than a clinical verdict — something the NHS has always maintained, since consumer wearables are not recognised as diagnostic devices by clinicians at NHS Kent and Medway or elsewhere. If the lawsuit prompts Oura to revise its marketing or app explanations globally, UK users may see changes to how the app presents sleep scores and accuracy claims. And if the case catches the attention of UK regulators such as the Advertising Standards Authority or the Competition and Markets Authority, it could lead to broader scrutiny of how wearable brands selling to consumers across Kent and the rest of the UK describe the health capabilities of their products.