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Apple Watch may be able to detect coronavirus infection days before tests can

Credit: Andrew O'Hara, AppleInsider

The Apple Watch may be able to detect if a wearer has coronavirus days before they are diagnosed or symptoms appear, a new body of research shows.

In some cases, wearable devices like Apple Watch or Fitbit devices can predict a COVID-19 infection even before a user becomes symptomatic or the virus is detectable by standard tests, according to studies from a number of leading medical institutions (via CBS News).

Medical researchers at Mount Sinai Health System in New York, for example, found that the Apple Watch can detect subtle changes in a user's heart rhythm up to seven days before an infection can be detected through testing.

The Mount Sinai study analyzed the variation in time between heartbeats, a metric known as heart rate variability. Researchers say it's a good measure of how a person's immune system is working.

"We already knew that heart rate variability markers change as inflammation develops in the body, and Covid is an incredibly inflammatory event. It allows us to predict that people are infected before they know it," said Rob Hirten, the author of the study and an assistant professor of medicine at the Icahn School of Medicine at Mount Sinai.

When it comes to COVID-19, individuals infected with the disease experience lower heart rate variability compared to those who tested negative. The study followed 300 health workers at Mount Sinai who wore Apple Watches for five months.

Notably, Apple highlighted the Mount Sinai study at its Apple Watch- and iPad-focused "Time Flies" event on Sept. 15, 2020.

Another study from Stanford University in California looked at a variety of activity and fitness trackers from Apple, Fitbit, Garmin, and other manufacturers.

That research, published in Nature Biomedical Engineering, found that 81% of those who tested positive for coronavirus experienced changes in their resting heart rates.

Like the heart rate variability metric, researchers found that the trackers could detect an infection up to nine and a half days before symptoms began.

According to Stanford University professor Michael Snyder, one of the main advantages of wearable trackers is that users wear them constantly throughout the day. That, Snyder said, could help do away with some of the disadvantages of standard coronavirus testing.

"The problem [with testing] is you can't do it on people all the time, whereas these devices measure you 24/7. The smartwatch gives you back the data right away, in real time, whereas if you're lucky you'll get your test back in a few days," Snyder told CBS.

The team also developed an alarm system that alerted users if their heart rate was elevated for a prolonged period of time. That could alert people to cancel going out or meeting others in-person, since they could be infectious. All of this research could help medical professionals and the public to stamp down coronavirus infections, since the majority of cases are spread by asymptomatic people.

"Right now, we rely on people saying they're sick and not feeling well, but wearing an Apple Watch doesn't require any active user input and can identify people who might be asymptomatic. It's a way to better control infectious diseases," Hirten said.