It’s well established that sleep quality is a fundamental pillar for healthy aging. Luckily, there is a growing universe of wearables we can use to better understand what is happening while we are asleep. Withings is a sleep tracking pad that goes under your mattress to measure sleep cycles, disturbances, and heart rate, Whoop and Biostrap are two wrist sleep monitors providing personalized reports, and the Fitbit Sense adds sleep to its wellness functions. Of the many options, our favorite (and seemingly the one preferred by longevity and biohacking experts like Peter Attia, David Sinclair, Dave Asprey, Ben Greenfield and the docs at Wild Health is the Oura Ring. Worn on a finger, it is unintrusive and accurate. We decided to dig deeper into Oura as a company and a product to understand why. This is what we learned.
The first thing that jumped out at us is the vision behind the company. According to Petteri Lathela, co-founder and Chief Innovation officer:
“we wanted to create something that would help people live to their real potential...something that would help people understand how their body is responding to their lifestyle, meaning their daily and long-term choices. We wanted to make this data visible for people so that it could empower them to make the kind of choices that would serve them best.”
This resonates clearly with us. We’re all about using data as a feedback loop on our bodies. It is a great foundation for N=1 experimentation that can help us troubleshoot our lifestyle choices. What gets measured can be improved and our bodies are no exception. In that context, Oura seems to have set out to build a “data mirror” of our lifestyle choices based on sleep and activity data.
Another insight that inspired Lathela to start the company is that he noticed how at a societal level the healthcare system in Finland, his home country, was not doing anything meaningful towards the prevention of the onset of chronic disease.
“Most people aren’t clear on what are the drivers of chronic disease. They may not know that prolonged stress is one of the big drivers for the onset of any kind of a chronic disease. There are many folks out there who are pre-diabatic and don’t know it. And we thought that sleep tracking could open a window into how your body responds to your daily lifestyle and provide that insight.”
This approach to long-term health outcomes, focused on prevention and early detection is something we strongly believe in. While it is only in the early innings, Oura clearly sees the potential of evolving into a data-driven, personalized preventative health device.
The credentials of the Oura team also seem to measure up to the challenge. From a core competence perspective, the company is located in the same hometown as Polar, the world’s pioneer in tracking wearables. In fact, Oura’s Chief Scientist happens to have been the lead scientist at Polar, where he worked for 18 years devising the algorithms needed to track and analyze heart rate monitoring data. So he knew exactly what he needed to build from the ground up.
So why a ring?
Oura’s CEO, Harpreet Rai explains that there were two factors that strongly favored the ring form factor. One is data fidelity: on the palm side of each finger we have two arteries that can be accessed using certain infrared wavelengths very effectively. So with a ring
“we get 50 to a 100 times stronger pulse wave signal that we can get from the wrist, for example.”
The second factor is compliance. A ring is one of the OG wearables, as people have been using them for thousands of years. You put it on and after a few days you don’t even notice it’s there. A chest strap might be a more accurate source of data, but few people would want to wear one every night. There is definitely a longitudinal benefit to having access to your sleep data. So getting an update every night is ideal.
How it works
The objective of the Oura ring is to help you understand how well you recover from your daily mental and physical strain. In this sense, Oura’s aim is very similar to that of Whoop, though they vary significantly in their approach. Oura tracks a number of signals including your pulse, heart rate variability, and body temperature. It picks up these signals through a set of infrared LEDs in the inside of the ring which shine tiny light pulses on your arteries. A photodiode sensor in the ring interprets the rates at which the light bounces back. The ring also has two negative thermal coefficient body temperature sensors, an accelerometer, and a gyroscope to track your movements. Core temperature is a key marker of how quickly you can fall asleep as well as how deeply. Activity tracking feeds into estimates of the level of strain you are undergoing during the day. It’s pretty amazing that you can fit all of this in a ring form factor. In fact, each new generation of the ring has gotten slimmer.
Every morning, the Oura ring crunches the raw data and gives you a Readiness Score based on how well you recovered overnight. It also breaks this out into a sleep assessment and a recovery index. The first is a detailed snapshot of your sleep quality built from 11 different data points including your pulse amplitude variation, breathing rate, core temperature and your physical activity from the prior two weeks. It also shows you how much you spent in each phase of sleep (lght, REM or deep sleep).
The recovery index is estimated based on when in the night your heart rate reached its lowest point. That is important because the sleep that you get after your heart rate bottoms out is the most restorative.
As far as measurement accuracy, Latherla says that ring’s heart rate and heart rate variability measurements are respectively 99.9% and 99.8% accurate compared to ECG readings. On temperature, the device is within 0.07 degrees centigrade of resolution, making it as effective as measuring temperature under your tongue.
When it comes to the derived signals like sleep state, the company benchmarks against the accuracy of a polysomnography (PSG), which is your standard sleep lab study. Oura is continuously working with sleep research labs to get ring biometrics to match those you can get in a sleep lab. We found one study published by the Stanford Research Institute comparing readings from Oura ring vs. their sleep lab PSG. On most measures, the data was very similar. The ring was shown to be less accurate in detecting different sleep stages. However, like all studies, context is important. Latherla has shared that the Institute bought two rings from their original Kickstarter batch and tested them on 41 subjects. He points that ring sizing might have been a big factor impacting accuracy (Stanford bought 2 sizes out of 8 offered).
Lastly, a couple of thoughtful design features jumped out at us. Oura seems to be the only one using infrared LEDs to measure your vitals. Most other wearables (Whoop, Fitbit, Apple Watch) use green lights. This might be relevant because it has been established that our skin is photosensitive and when you shine a light on it, your REM sleep can be disturbed. This doesn’t happen with infrared wavelengths. Can a small, steady exposure to green light in the back of your wrist disrupt your circadian rhythm? Potentially. In any event, Oura present an alternative way to collect your biometric data.
If you are concerned about exposure to the electromagnetic waves coming from the ring’s bluetooth, you can switch it to airplane mode and it will store up to 6 weeks of data without having to sync. Finally, it compares you to you. It takes two weeks to generate enough data to create a baseline metric and then it measures changes in the body and sleep to determine deviations from baseline.
Having analyzed millions of sleep nights from users across the world, the Oura team has found that one of the key drivers of sleep quality is consistency in the time when we go to sleep. They've been able to compare the sleep quality of folks whose bedtime is consistent throughout the week vs. others who go to sleep much later in the weekends and found that the latter group had a consistently higher resting heart rate all the time. They also noticed that optimal bedtime could range pretty widely amongst users. To help you optimize, the Oura app reminds you when it is time to get ready for bed. During the day, the ring prompts you to move around if it senses you’ve been stationary for too long.
Most importantly, we think the ring is a good feedback mechanism for you to run n=1 tests on to help you discover connections between your lifestyle behaviors and outcomes. For example, you can try different kinds of bedtime routines, or supplements and see how your body responds, so you can calibrate as you go along.
My, look at all this data.
We think that data may turn out to be Oura’s killer advantage. The company has already sold more than 500,000 rings, 350,000 more rings than a year ago, and given that they have been embraced by the longevity and performance communities, that growth is likely to accelerate. As they gain users they also get the data and insights they need to make their product better. Lathela has said that only a fraction of the insights they have learned thus far are reflected in the product:
“We humans are pretty complex, there are so many things that affect us mentally, physically, cognitively...There's so much we can still learn about the different aspects of sleep and recovery. In fact, we are expanding the thinking of rest and load so we observe more than sleep time. We have resting and recovery moments during the day for example. We are therefore building a 24/7 model that helps us ask when it would be optimal for you to take a nap or do your meditation or walk outside in nature and then reflect back on how that affected your readiness and your next night’s sleep and ultimately be able to build a long-term causal relationships between factors.”
All of this suggests that we can expect the Oura ring to get smarter and more accurate over time. The company really seems to be in the early innings of building a very sophisticated preventative health device and investors definitely seem to agree. The company recently raised $100 million from investors, tripling their previous total funding with a valuation of $800 million. They have developed partnerships with a number of athletic groups including the NBA, WNBA, UFC, NASCAR, and most recently the U.S. Olympic Surfing Team. Their temperature monitoring technology has been pushed to the forefront of UCSF health research after it became a possibility to link temperature changes to COVID-19 infections among other health issues. Women have been able to use it to predict menstruation, which normally is done with a basal body thermometer. The pandemic also prompted a boost in demand for wearable health trackers including the Oura Ring making 2020 their first year of profitability.
Putting all of this together, we think the Oura ring is a worthwhile tool to have in your longevity toolbox. It is not approved as a regulated medical device but is a consumer friendly bridge between health and habits. You can find out more here.