New medical studies from leading institutions have found that wearable technology can help detect coronavirus infections days before the first COVID-19 symptoms appear.

According to research conducted by the likes of Mount Sinai Health System in New York and Stanford University in California, subtle changes in an individual's heartbeat can be symptomatic of coronavirus infections up to seven days before people knew they were sick.

Apple did not fund the study nor has it participated in it.

Spotting COVID-19 in a Non-invasive Way

The studies have focused on heart rate variability, a metric captured by the Apple Watch and similar smartwatches. Heart rate variability is the variance in time between the beats of one's heart. As a metric, heart rate variability can indicate how well your immune system is working---high values indicate that your immune system is more active than usual.

Published in Nature Biomedical Engineering, the study involved 32 coronavirus-positive individuals out of more than 5,000 participants. Using just smartwatch data, researchers were able to spot nearly 66 percent of COVID-19 cases four to seven days before diagnosis.

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Rob Hirten, assistant professor of medicine at Mount Sinai's Icahn School of Medicine, told CBS how these subtle heartbeat changes can indicate COVID-19 before diagnosis:

We already knew that heart rate variability markers change as inflammation develops in the body, and COVID-19 is an incredibly inflammatory event. It allows us to predict that people are infected before they know it.

Specifically, coronavirus-positive participants were found to have lower heart rate variability. The study logged Apple Watch data from nearly 300 Mount Sinai healthcare workers who were tasked with wearing Apple's wearable between April 29 and September 29, 2020.

Detecting Asymptomatic Cases

In a separate study from Stanford, participants wore wearable devices from Apple, Garmin, Fitbit, and others. A whopping 81 percent of participants who have tested positive for COVID-19 have experienced resting heart rate changes almost ten days before developing symptoms.

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Good news for Apple customers: that study has discovered that wearing an Apple Watch can also help identify asymptomatic cases. This is especially important knowing that asymptomatic carriers are responsible for more than half of all coronavirus infections.

The Apple Watch provides a feature that monitors your heart rate intermittently in the background, showing you a notification if your heart rate has been elevated for a sustained period of time.

While designed to help identify various heart conditions, Apple could adapt the feature to help spot COVID-19 symptoms ahead of time. After all, CEO Tim Cook mentioned Mount Sinai’s study during the company’s recent virtual product launch event.