Fitness trackers can tell you how well you’re sleeping, how fast you’re walking and, of course, how many steps you’ve taken.
But during the pandemic, researchers have also investigated the ability of smartwatches to help detect COVID-19 or provide data on recovery.
The latest study uses several measures of heart rate data to help track the progression of symptoms in someone who has the coronavirus and to show how sick that person becomes while ill.
How fitness trackers may help
In the study, fitness trackers detected that COVID-19 dampened biological timekeeping signals, says co-author Daniel Forger, a mathematics professor at the University of Michigan, in Ann Arbor. The researchers also found signs of changes in how a person’s heart rate responds to activity, altered resting heart rate and stress signals.
“Most people using this data think about heart rate as one number, but heart rate is this vital sign that reflects so many different physiological processes,” Forger shares. “That’s what our goal is as mathematicians, can we take this one string of numbers, all these heartbeats, with all the noise and everything and say something about different physiological signals?”
While past research has included working to understand disease through wearable heart rate data, for this effort the researchers focused on breaking down the heart rate signal into parts.
The team used data from the 2019 and 2020 cohorts of the Intern Health Study, which follows physicians during their first year of residency, and the Roadmap College Student Data Set, which looked at student health and well-being during the 2020-2021 academic year. Students in that study wore Fitbits and self-reported COVID-19 diagnosis and symptoms.
This new study included 43 medical interns and 72 undergraduate and graduate students who had a positive COVID-19 test. They had been wearing their fitness trackers 50 days before symptoms and 14 days after.
The researchers found that when COVID symptoms began, the study participants had a heart rate increase per step. This heart rate per step was significantly higher for individuals who had a cough.
A person’s daily resting heart rate increased when symptoms started or before, possibly because of fever or increased anxiety, the researchers suggest.
As COVID-19 symptoms started, individuals had increased “circadian phase uncertainty,” which is the body’s