Wearables and temperature monitoring – the full story – Wareable | Hot Mobile Press

Some of the biggest names in wearables, including Fitbit, Oura, and Whoop, have added temperature tracking to their devices.

And rumors suggest Samsung’s next Galaxy smartwatch and Apple Watch Series 8 could be next. But what are the benefits?

Portable thermometers — also called permanent thermometers — have been around in hospitals and medical facilities for years.

“Temperature tracking wearables can continuously and seamlessly collect data and record temperature trends,” says Professor Hossam Haick, an expert in nanotechnology and non-invasive disease diagnosis.

“They automatically notify when physician-set high-temperature thresholds are exceeded.”

But outside of medical care, what’s the point of tracking your temperature 24/7? Why should we have a temperature sensor on our Apple Watch? We found out.

Core body temperature vs. skin temperature

Taking your temperature is confusing because it’s not consistent throughout your body.

We spoke to dr. Chris Tyler of the University of Roehampton, who specializes in human responses to extremely hot and cold environments.

He says the holy grail of temperature measurement is hypothalamic temperature — that’s your brain’s temperature. But measuring the temperature of your other major organs offers the same high level of accuracy. This is your core body temperature.

However, measuring brain temperature is not easy in a laboratory setting, let alone anywhere else. For this reason, the most common temperature reading is your peripheral body temperature.

This is usually measured from the mouth, ear, armpit, or rectum. However, all of these locations do not provide the same readings. “The more indirect the method, the less accurate it is,” said Dr. Tyler.

We can also measure skin temperature, which is sometimes lumped with peripheral body temperature but tends to be less accurate than other methods.

“Skin temperature and body temperature can have a relationship.” However, he explains that skin temperature measurement is external and can be affected by your environment.

“All you have to do is wear a hat, go for a walk, or stand in a breeze for a few minutes and the relationship is warped.”

And when it comes to wearables that live on the skin, that poses an accuracy challenge. And we’ve seen utility issues, too. Some budget smartwatches from Amazfit GTR 3 and Huawei Watch GT 3 have built-in skin temperature function. However, these were simple temperature readings with no context, long-term averages, or any way for users to understand the data. In short, pretty much useless.

However, there are more innovative approaches.

Find your baseline

Find your baseline

A number of newer Fitbit devices — Fitbit Sense and Charge 5 (and Charge 4) — measure your skin temperature throughout the night to determine your average temperature.

After three nights, the Fitbit app gives you a personal skin temperature baseline and range. Instead of generating a skin temperature number, which Dr. Tyler bears little resemblance to your core temperature, the wearable looks for deviations from what’s normal.

“Your baseline is used to provide insight into when your skin temperature is higher or lower than your baseline and whether it’s within your personal range, since it’s natural for your skin temperature to vary from night to night,” says Dr. Fitbit’s Conor Heneghan says.

You can then look for temperature changes outside of your personal range.

“This can help you understand changes in your body, like the start of a new menstrual phase, or detect possible signs of fever or illness,” explains Dr. heneghan

“Skin temperature shouldn’t replace a thermometer that measures core temperature,” he tells me. “However, it can act as a warning sign that something has changed.”

Both the Oura Ring 3 and Whoop 4.0 measure similar skin temperatures. This data is combined with everything else they know about you to make recommendations and better inform how ready you are for the day ahead.

Interestingly, the Oura Ring was used in a Covid-19 study called TemPredict. The results suggest that the Oura Ring temperature data — combined with all other data collected — could help detect the early signs of Covid-19 infection in participants 2.75 days before they felt sick enough to develop to take a test to find out.

These results are exciting for the future role wearables could play in disease tracking. But we still shouldn’t treat our wearables like doctors, they might give us a great “red flag” but not the whole story.

Menstrual and ovulation tracking

Menstrual and ovulation tracking

There is tremendous potential for using temperature data to predict menstruation and ovulation, as body temperature rises slightly during ovulation.

In 2019, Oura conducted a small pilot study on the effectiveness of menstrual and ovulation tracking using temperature data from the ring. The results were promising. Menstruation was detected with a sensitivity of 71.9 – 86.5% and ovulation with a sensitivity of 83.3%.

Fast forward to 2021 and the company has since rolled out a beta feature called Period Prediction. For people who are menstruating, this combines manually entered data about the start and end dates of their period and temperature data to predict with greater accuracy when their next period will arrive.

Oura is not focused on ovulation at the moment. But for wearables company Ava, tracking ovulation and fertility is paramount.

Many people are currently tracking their fertility by using a thermometer first thing in the morning to determine their basal body temperature (BBT). A slight rise in temperature is usually a sign of ovulation.

But Ava is a smarter and less complicated solution. While you’re sleeping, it takes the skin temperature on your wrist, and then you’ll see a fertility prediction from the app when you wake up. And was used in 2020 Covid-19 detection trials.

We’ve already learned that skin temperature isn’t the most accurate form of temperature measurement — particularly for accurately detecting fevers and heat-related illnesses. However, a 2021 study suggested it might be more sensitive than BBT specifically for ovulation tracking.

Fitbit skin temperature reading

Ava combines temperature readings with resting heart rate, heart rate variability, respiratory rate, and skin perfusion data.

“We were the first to study the effect of multiple physiological signals measured continuously throughout the menstrual cycle,” Lea von Bidder, co-founder and CEO of Ava, told Wareable.

She explained that research used to track different signals in isolation, but not all of them and not continuously. “Wearable technology allows for much broader measurements and advanced analysis,” she said.

Ava’s machine learning algorithms then use all of this data to identify a five-day fertile window — which Lea von Bidder says is 90% accurate. It’s also much more helpful, as von Bidder tells us, that other methods identify the date of ovulation, which marks the end of the fertile window.

While many mainstream wearables offer menstrual cycle tracking, few have used skin temperature analysis to do so. Most implementations use self-entered data to predict when the next cycle will occur – rather than biometric data.

The future of temperature tracking

Amazfit displays temperature

When we asked the experts about the future of wearable temperature measurement, the answer was the same: improved algorithms.

Several recent studies have examined how algorithms could be used to predict a person’s core body temperature using only a skin temperature measurement.

But we’re not there yet. dr Tyler tells us he’s currently working with a company to improve their algorithms and incorporate different data points — heat flow and heart rate — to make temperature readings as accurate as possible.

“Currently, forecasts are only good enough in fairly small (and stable) ranges,” he tells us.

Ava’s future focus is to roll out its algorithms to more hardware.

“We are actively exploring the possibility of bringing Ava’s technology to other wearables,” says von Bidder. “That will help us make it more accessible.”

Issy Towell, a wearables analyst at CSS Insight, told us that she hopes similar temperature-tracking wearables will support women at even more stages in their lives, including postpartum or treating symptoms of endometriosis or menopause.

“The potential for women’s health applications can be life-changing for many women around the world if skin temperature measurements become accurate enough to help women understand what’s going on inside their bodies,” she tells us.

But she does point out a common technical issue that could get in the way — battery life.

“Part of the fight is making wearable devices that can be worn at all times so that there is enough data to create a robust baseline for personal temperature,” she said.

Should we be excited about temperature tracking?

Amazfit skin temp

With hardware and software improvements, temperature measurement could become more accurate and useful.

But does anyone need to track their temperature with a wearable now? It depends on.

If you are looking for a fertility tracking solution, Ava presents a clear use case that is an improvement over other traditional methods.

For everyone else who uses their smartwatch, ring, or activity tracker for general temperature tracking, the benefits are less clear. Knowing when you’re sick is an obvious application, but how useful is this data when we’ve found that changes in temperature tend to delay symptoms.

The data will be fascinating to those interested in learning more about their health and fitness and who like to spot patterns.

For others, the information might be a bit pointless until it’s packaged in a more meaningful and actionable way. “The problem with providing large amounts of skin temperature data to consumers is that not all consumers want to become hobbyists of data science,” says Towell.

Until then, there’s nothing wrong with using a wearable to also track your workouts, heart rate, steps and temperature.

But we need the algorithms and analytics to match the sensor data — and until then, we won’t be enjoying the fruits of this new wearable revolution.

Leave a Comment