Body temperature is one of the most popular indicators of our current health – if you’re getting sick, elevated body temperature can be one sign of it. Long-term body temperature tracking can also give us insights into our body. It’s used in e.g. menstrual cycle and recovery follow-up.
Oura’s solution is nocturnal skin temperature tracking that concentrates on temperature deviations and trends.
Especially in long-term tracking, a method that provides as comfortable and unobtrusive measurement as possible is, of course, much appreciated. Oura’s solution to this requirement is nocturnal skin temperature tracking that concentrates on temperature deviations and trends.
The Oura ring includes a NTC temperature sensor, in addition to other body signal tracking technologies it utilizes. When you sleep with the ring on your finger, the sensor quietly registers your skin temperature reading every minute.
The ring automatically detects the time when the skin temperature corresponds to your body temperature. Oura compares this value to corresponding values from earlier nights – your body temperature baseline. In the Oura app, you’ll see the nightly deviation from your baseline. You can see your long-term trends also in Oura Cloud.
Oura conducted a validation study to assess how well the nightly skin temperature readings provided by the Oura ring associate with oral temperature readings taken immediately after wake-up. The study evaluated how Oura’s body temperature measurement could be utilized in fertility tracking. Therefore it concentrated on women, and analyzed separately the pre-ovulation and post-ovulation phases of women’s menstrual cycle. The sample consisted of 5 healthy women across their menstrual cycle.
The deviation of the Oura temperature corresponded with that of oral body temperature both in pre-ovulation and post-ovulation phases.
The results showed similarity in body temperature readings between the Oura ring and oral thermometer. The deviation of the Oura temperature (0.16±0.02°C and 0.19±0.03°C) corresponded with that of oral body temperature (0.15±0.04°C and 0.18±0.05°C) in pre-ovulation and post-ovulation phases, respectively.
The sample of the study was small, but it also gave initial insights into fertility tracking. The body temperature readings measured by the Oura ring differed clearly (strong statistical significance) between pre-ovulation phase and post-ovulation phase in 3 out of 5 test subjects. Note that using hormonal birth control may suppress the monthly temperature variation, as was the case with 1 of the 5 subjects in the study.
Oral body temperature showed a clear difference (strong statistical significance) in 2, and smaller yet significant difference (statistical significance) in 2 subjects.
The results are promising in respect of detecting the fertility time points, even though further studies are needed to confirm the findings. Furthermore, the Oura ring can improve the accuracy of tracking, because it gathers also other applicable body signal data ranging from resting heart rate to nocturnal respiration rate.
In the image above, you can see an example of what fever looks like in the Oura app. If you notice a sudden rise in your body temperature trend, measuring your body temperature with a thermometer is a good idea.
You can also notice a deviation caused by menstrual cycle phases in your longer term Oura app data.
Speaking about the menstrual cycle, our Chief Scientific Officer Hannu Kinnunen has a tip from research to all you athletes and coaches out there:
“It would be beneficial for female athletes and their coaches to take menstrual cycle phases into account when planning training and competition schedules. A recent study regarding female athletes, conducted at Umeå University in Sweden, suggests that optimal strength training benefits can be achieved by scheduling highest training loads to pre-ovulatory period, and by avoiding overload during the latter half of the menstrual cycle.”
If you’re interested in tracking your nocturnal body temperature trends and other readiness metrics, and you don’t yet have the tools for it, have a look at the new Oura ring in the Oura Shop. If you have an Oura ring, you can also dig deep into your nocturnal body temperature trends in the Oura Cloud.
In the third part of our guest blog series, our prestigious visiting writer Dr. Benjamin Smarr discusses the influence of age on our circadian preferences: how sleep changes across a lifetime.