Since the onset of the COVID-19 pandemic, a handful of studies have set out to determine whether wearables such as the Apple Watch can detect early signs and symptoms of COVID-19. A new paper published today in the journal JAMA Network Open highlights that wearables like the Apple Watch and Fitbits could also provide data on the long-term effects of COVID-19.

As reported first by the New York Times, the new data comes from the Digital Engagement and Tracking for Early Control and Treatment (DETECT) trial run by scientists at the Scripps Research Translational Institute in California. This study ran from March 25, 2020 through January 24, 2021 and included more than 37,000 people using Fitbits, Apple Watches, and other wearables. The study was powered by the MyDataHelps research app.

The researchers first reported in October that combining data from the Apple Watch and Fitbit with self-reported symptoms led to more accurate detection of COVID-19 cases than purely focusing on symptoms.

Now, researchers are diving deeper into the data with a focus on the lasting health effects of COVID-19 — oftentimes referred to as “long COVID.” At first, the researchers are focusing on data from Fitbit users, which shows that Fitbits can detect lasting changes. “There was a much larger change in resting heart rate for individuals who had Covid compared to other viral infections,” said Jennifer Radin, an epidemiologist at Scripps. “We also have a much more drastic change in steps and sleep.”

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While this subset of research focuses on Fitbit data, Dr. Radin says that more research like this is planned for the future.

The scientists also found that about nine days after participants with Covid first began reporting symptoms, their heart rates dropped. After this dip, which was not observed in those with other illnesses, their heart rates rose again and remained elevated for months. It took 79 days, on average, for their resting heart rates to return to normal, compared with just four days for those in the non-Covid group.

Sleep and physical activity levels also returned to baseline more slowly in those with Covid-19 compared to those with other ailments, Dr. Radin and her colleagues found.

The researchers identified a small subset of people with Covid whose heart rates remained more than five beats per minute above normal one to two months after infection. Nearly 14 percent of those with the disease fell into this category, and their heart rates did not return to normal for more than 133 days, on average.

You can find the full paper in the JAMA Network Open journal and read more at the New York Times.

“We want to kind of do a better job of collecting long-term symptoms so we can compare the physiological changes that we’re seeing with symptoms that participants are actually experiencing,” Dr. Radin said. “So this is really a preliminary study that opens up many other studies down the road.”