To kick off our series of sensor and digital health technology reviews we took a look at the ŌURA ring – a smart ring which claims to be ‘the most accurate, comfortable and beautiful wearable available’. The question is, in a wearables market that is full of big competitors and even bigger claims, can the ŌURA ring sustain being put through the ringer…..
As will be the case with all our reviews, we will be leveraging the evaluation framework for human performance measurement technologies published in Nature Digital Medicine. An overview of how these reviews will be conducted was published on our blog last week.
What is the ŌURA Ring and what does it do?
The ŌURA ring is a smart ring, designed to be worn on any finger (8 sizes available) and ‘help you get more restful sleep and perform better’. It strives to do this by collecting data about body temperature (negative thermistor sensor), heart rate [HR]/heart rate variability [HRV] (polysomnography) and activity/sleep tracking (tri-axial accelerometer and gyroscope). It is designed to be used in conjunction with a free android or iOS mobile app.
The ring provides you with metrics about sleep, activity and readiness.
Who makes the ŌURA ring?
The ŌURA ring is a piece of wearable jewellery developed by ŌURA Health OyLtd, a health technology company founded by Kari Kivelä, Markku Koskela and Petteri Lahtela in Oulu, Finland in 2013. To date, the company has received upwards of $33 million in funding over four rounds and has an estimated annual revenue of approximately $2 million. Sports and TV fans might be interested to know that investors include the likes of Lance Armstrong, Shaquille O’Neal and Will Smith.
How much does it cost and where can I buy it?
Those interested in the ŌURA ring have a selection to choose from, ranging from the ‘Silver’ and ‘Black’ options (€314), to the ‘Stealth’ option (€419) to the diamond version (€1049). The ring is available internationally online, with no minimum or maximum order requirements. Importantly, the company will play import taxes for EU and USA customers only, while customers outside of this will have to fork out for the taxes themselves.
What is the science behind the ŌURA Ring?
Given the big claims by ŌURA that it is ‘most accurate, comfortable and beautiful wearable available’, does the science live up to the hype?
There are currently three papers available which have evaluated the validity (ability to measure what it’s supposed to measure) of the ŌURA ring. One internal white paper on the accuracy of the HR/HRV and two papers (one peer-reviewed paper and one internal white paper) on the accuracy of the sleep/ sleep quality estimations
Firstly, the internal white paper comparing nocturnal HR and HRV to the gold-standard Echocardiogram [ECG] measurement:
- Ten healthy adults wore the ŌURA ring and a Faros 360 ECG device (Mega Electronics, Kuopio, Finland) over-night. Individuals wore the smart ring on each hand.
- The ŌURA ring software labelled inter-beat intervals to estimate HR and HRV, while the Kubios software was used to obtain the comparison reference HR and HRV.
- Pearson correlation was then used to investigate the relationship between the two measures.
- The authors reported ‘ŌURA Ring provided reliability as compared to ECG of (r = 0.999) and (r = 0.984) for HR and HRV, respectively’.
While the authors conclude that ‘The nocturnal resting HR and HRV numbers measured by the ring represent similar values to those derived from the ECG’, we have a couple of major issues with the methods used:
- This paper only focused on nocturnal HR and HRV, arguably the easiest time to quantify this, not taking into account the accuracy during bouts of activity throughout the day – this would likely reduce the accuracy of the estimates.
- This analysis is only based on periods where 50% (HR) and 30% (HRV) of the intervals were labelled as ‘normal’. However, they don’t provide information on how often the ŌURA ring labelled data as abnormal. To me this is essentially cherry-picking nice clean data for comparison, ignoring the ‘abnormal’ data.
- This is a statistical point, but one we cannot ignore. The authors conclude that the ring can provide ‘reliability as compared to ECG’. This is not true. What the authors did do, was show a high correlation between the ring’s estimations, but did not (as they have stated) demonstrate ‘reliability’ or indeed ‘agreement’ – that requires a completely different type of analysis.
In short, this internal paper showed that when they exclude unwanted ‘abnormal’ data, the ŌURA rings estimations of HR and HRV have a high correlation with the gold standard ECG; however, I would be intrigued to see what the accuracy of the measurement would be if they didn’t simply exclude unwanted data.
Secondly, an external peer-reviewed paper on the accuracy of the sleep/ sleep quality estimations published in the journal of Behavioural Sleep Medicine. This study was conducted by an external research group based in California and provides a decent unbiased analysis of the sleep estimation.
- Forty-one healthy adolescents/ young adults wore the ŌURA ring in a single laboratory overnight.
- Sleep data were recorded using the ŌURA ring and the gold-standard polysomnography [PSG].
- The ŌURA ring metrics were compared to the PSG equivalent using Blant-Altman and epoch-by-epoch analysis.
- The authors concluded that the ŌURA ring tended to underestimate Deep Sleep (approx. 20 min) and underestimate rapid-eye-movement (REM) sleep (approx. 17 min). Total sleep time and wake after sleep onset lay within the ≤30 min a-priori-set clinically satisfactory ranges for 87.8% and 85.4% of the sample, respectively.
- The ŌURA ring could detect sleep 96% of the time (excellent) but could only detect waking 52% of the time (poor). Additionally, agreement in detecting the stages of sleep (light, deep and REM sleep) was poor, ranging from 51-65%.
Interestingly, the authors conclusions about the ŌURA ring are relatively kind:
“Multisensor sleep trackers, such as the ŌURA ring have the potential for detecting outcomes beyond binary sleep-wake using sources of information in addition to motion. While these first results could be viewed as promising, future development and validation are needed.”
However, we’d like to draw your attention to a few key aspects related to the results of this study:
- While the ŌURA ring was excellent at detecting sleep, the sophisticated flipping a coin method would have similar accuracy in detecting wake, based on this study.
- While there was an underestimation for light sleep (approx. 4 min), underestimate deep sleep (approx. 20 min) and underestimate REM (approx. 17 min), the Bland-Altman analysis highlights just how much the ring differed from the gold-standard measure. For example, the ŌURA ring overestimated deep-sleep by as much as ≈100 min and underestimated it by as much as ≈65 min. Seeing as the average deep sleep time was only 97 min, this shows a marked (and non-systematic) difference between the ŌURA and the gold-standard alternative. Similar findings are seen for REM sleep estimation.
In other words, the ŌURA ring can accurately detect sleep, but is pretty poor at detecting wake and the various different stages of sleep. Based on this, and contrary to the authors conclusions, I would argue that the ring is not very good at detecting sleep outcomes ‘beyond binary sleep-wake’.
What happens to the raw data and can I access it?
A common trait that we see within the consumer wearables space is a lack of information related to the nature of their algorithms and whether raw sensor data can be obtained from the device. The ŌURA ring is no different, with no clear information provided about the methods used in the data analysis and if the user can in-fact access the raw sensor data. While the user can access the summary metrics through the mobile application, for research purposes, this may not be enough.
As with many consumer wearables, ŌURA are attempting to try to make sense of the data capture by the ring through a composite ‘Readiness’ score; a metric derived from sleep, activity balance, body temperature and resting heart rate. This is a common theme across the health and wellness tech sector, however we’ve yet to see anyone develop any magic score that is actually related to injury, illness or any other factor for that matter.
What about human factors?
With the statement that the ŌURA is the ‘most accurate, comfortable and beautiful wearable available’, one would assume that the ŌURA has undergone some rigorous user testing. While they do provide quite a detailed overview of their design process on their website, there is no objective published data on this.
Aside from this, the ring requires little interaction apart from the obvious wearing of it, synching the data through the mobile application and wirelessly charging the device. In fact, one of the most impressive aspects of the smart ring is the ability of the company to have shrunk this set of sensors into such a small device that boasts an impressive week-long battery life. It will be interesting to see where this technology brings us in the next 10 years.
Is it being used in any clinical trials?
As one of the biggest interests in our research group is essentially understanding how technology can be used to improve health and performance, we are always interested to know if the technology in question is being used in any clinical trials.
Currently, there have been no published clinical trials which have leveraged the ŌURA ring; however, there is one registered trial of 1060 participants currently underway seeking to develop a set of typologies of users of mobile sleep tracking technologies, and optimal sleep health educational strategies among users of mobile wearable technologies that track sleep.
The bottom line
The ŌURA ring boasts itself as the ‘most accurate, comfortable and beautiful wearable available’. While you may agree that it is indeed ‘comfortable’ and/or ‘beautiful’, based on this evaluation of the current evidence available, it is hard to fully agree with the statement that it is ‘accurate’ – especially if you are looking to get detailed information about the stages of sleep. The ring is not cheap, coming in at €314 – €1049, a substantial price to pay considering you could arguably get a wearable with similar accuracy, for substantially cheaper. However, if a ring-based wearable is more desirable than a wrist-worn one, then the ŌURA may be suitable for your needs – but only if you are looking for high-level activity, sleep and HR data. It will be fascinating to see the outcome of the ongoing clinical trial using the ŌURA ring, and see where the technology goes over the coming years.
If you have any questions about this Digital Health Tech review, the research conducted by our group or the Digital Health Technology Evaluation Framework, please contact us via the blog or twitter!
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