Sleep Tracking Ring May Detect When You’ve Drank Too Much

Infrared LEDs hidden inside the band measure the heart rate while at rest, as well as a temperature sensor to sense variation in body heat, along with a 3D accelerometer to track day time activity; and while you are sleeping electronics on the inside of the band sample your pulse 250 times per second to track strength of heartbeat and heart rate variability so that its algorithms can derive insights regarding sleep quality.

“We wanted to develop something that would help people understand how their body responds to their lifestyle. We are putting the sleep lab into the normal daily life context, ” says Co-founder and president Petteri Lahtela.

Inspired by pulse oximeters that clip onto fingers which are commonly used in hospitals the team created a ring design because wrist devices are not accurate enough and belts are too uncomfortable to wear for extended periods of time. 

“There are two arteries on the palm side of each finger,” says Lahtela. “We noticed that by using certain wavelengths of infrared light, we can get access to those arteries and get very good signal strength.”

When comparing the ring to polysomnography SRI International found the ring could detect when the wearer was asleep up to an accuracy of 96%, but could only detect the different sleep stages up to an average of 60% accuracy, with a 48% specificity for detecting wakefulness relative to PSG. Basically it’s a coin flip as like other sleep sensors utilizing actigraphy in most individuals it is not able to differentiate between time you are awake lying still and when you are asleep and lying still. 

“You can then see how your lifestyle changes affect your sleep quality,” says chief scientific officer Hannu Kinnunen. “When you wake up and connect the ring to the app via Bluetooth, you can see your overall sleep time, resting heart rate and a breakdown of sleep stages. You are also given an overall sleep score, and a “readiness” score, which rates how prepared you are for the day ahead. The app offers advice based on your sleep performance and, after gathering enough data, suggests an optimal bedtime.”

Victoria Turk writes in Wired, “I tried out the ring at Slush tech conference in Helsinki, where a nurse from the Finnish Institute of Occupational Health, hooked me up to a PSG system so that I could compare the results... When I showed the Oura team my app readings the next morning, they could immediately tell from a spike in my heart rate early in the night that I’d had a couple of glasses of wine before bed (although they kindly suggested this effect could also be caused by a heavy meal or over-exercising). The Oura results followed the same general pattern as the PSG, although this anomaly threw the ring’s readings off somewhat, partly because it had not yet had chance to establish my baseline.” 

“Wearing the ring over a longer period, I soon picked up on trends in my sleep habits. On days I went to bed later than usual I got less REM sleep, and an evening in the pub would betray itself in my resting heart rate graph the following morning. The point of showing this information, Lahtela says, is to help people make their own lifestyle changes – going to bed earlier, sleeping longer, avoiding unhealthy activities – that they can then see the impact of,” says Turk. 

The ring is now in its second generation, and due to the popularity it currently has a 9-12 week waiting period for new orders; popularity may have been inspired when Prince Harry was spotting wearing one during a tour in Australia. 

The company plans to keep improving their design and user experience by adding new features based on anonymised data that has been gathered from users so far. “Once you realise what sleep can do for you, it’s really motivating,” says Lahtela. 

The ring does have faults/limitations and skeptics such as cardiologist Anthony Pearson who reviewed the pricey ring and published his own findings in MEDPAGE TODAY:

“Despite Oura's tantalizing claims, there is only one legitimate scientific comparison of the ring to the gold-standard of sleep evaluation, polysomnography (PSG). In addition, there is no published evidence whatsoever that changing one's behavior based on the various parameters that the ring produces will have any favorable effect on your sleep quality or health in general.” says Pearson.

“Over several months of using the ring and app, I have found little relationship between how I feel after sleeping versus how Oura has rated my sleep. There is even less correlation between the "readiness" score that Oura produces and how I feel during the day. Overall, I have found absolutely no actionable information from my months of using the ring. Now, I am just one individual. It is entirely possible there is something unique about my sleep that invalidates the ring's accuracy.”

"Clearly, further work is needed to determine what combination of sensors might be used to optimally develop an algorithm that differentiates sleep stages sufficiently well to detect real differences or changes in healthy and clinical populations.” “If you are hoping to get improved analysis of your sleep quality, I don't think Oura adds anything to what is elsewhere available using cheaper wrist actigraphy devices."

“I'm intrigued by some of the cardiovascular data it produces. Although I don't think the data can guide me to healthier behavior, it's possible that there is useful information in there somewhere. I've done research in this area and have some strong opinions on its value. I'm curious to see if the respiratory rate data and the temperature data is of any value whatsoever. So, the ring is best I would say for well-heeled, self-hacking, and self-experimenting techno geeks.”