Last spring, as the country’s Covid-19 cases skyrocketed and tests were running out, some scientists wondered if a new approach to disease surveillance could be on Americans’ wrists.
One in five Americans uses a Fitbit, Apple Watch, or other portable fitness tracker. And over the past year, several studies have indicated that the devices, which can continuously collect data on heart rate, body temperature, physical activity, and more, could help detect early signs of Covid-19 symptoms.
Research now suggests that these wearables can also help track and provide insights into patients’ recovery from the disease its long term effects.
In a paper published Wednesday in JAMA Network Open magazine, researchers who examined Fitbit data reported that people who tested positive for Covid-19 had behavioral and physiological changes, including increased heart rates that last for weeks or months could. These symptoms lasted longer in people with Covid than in people with other respiratory diseases, the scientists found.
“That was an interesting study and I think it’s important,” said Dr. Robert Hirten, gastroenterologist and wearables expert at the Icahn School of Medicine on Mount Sinai, who was not involved in the new work. “Wearable devices offer us the possibility of inconspicuously monitoring people over long periods of time in order to see objectively – how has the virus really affected them?”
The results come from the Digital Engagement and Tracking for Early Control and Treatment (DETECT) study conducted by scientists at the Scripps Research Translational Institute in La Jolla, California. From March 25, 2020 to January 24, 2021, more than 37,000 people have enrolled in the process.
Participants downloaded the MyDataHelps research app and agreed to share data from their Fitbit, Apple Watch, or other portable device. They also used the app to report disease symptoms and the results of Covid-19 tests.
In October, the same researchers reported in Nature Medicine that they could detect Covid-19 cases more accurately if they combined wearable data with self-reported symptoms than if they analyzed the symptoms alone.
But the data, the researchers found, could also help them keep track of what happened to people after the worst illness was over. People recovering from Covid have reported a variety of long-term health effects, including fatigue, “brain fog”, shortness of breath, headache, depression, palpitations, and chest pain. (These persistent effects are often referred to as long covid.)
The new study focuses on a subgroup of 875 Fitbit-wearing participants who reported a fever, cough, body aches, or other symptoms of a respiratory disease who were tested for Covid-19. Of these, 234 people tested positive for the disease. The rest probably had other types of infections.
Participants in both groups slept more and walked less after they got sick, and their resting heart rate rose. But these changes were more pronounced in people with Covid-19. “There was a much greater change in resting heart rate in people who had Covid compared to other viral infections,” said Jennifer Radin, epidemiologist at Scripps who leads the DETECT study. “We also have a much more drastic change in step and sleep.”
The scientists also found that about nine days after participants with Covid first reported symptoms, their heart rate dropped. After this dip, which was not seen in other illnesses, her heart rate rose again and remained elevated for months. It took an average of 79 days for their resting heart rates to return to normal, compared to just four days for those in the non-Covid group.
July 9, 2021, 6:08 p.m. ET
This persistent increase in heart rate can be a sign that Covid-19 is disrupting the autonomic nervous system, which regulates basic physiological processes. The palpitations and dizziness that many people report when recovering from Covid can be symptoms of this disorder.
“Many people who get Covid end up developing autonomic dysfunction and some sort of persistent inflammation, and this can affect their body’s ability to regulate their heart rate,” said Dr. Radin.
Sleep and physical activity also returned to baseline more slowly in patients with Covid-19 compared to those with other complaints, found Dr. Radin and her colleagues out.
The researchers identified a small subset of people with Covid whose heart rate stayed more than five beats per minute above normal one to two months after being infected. Almost 14 percent of sufferers fell into this category, and their heart rate did not normalize for more than 133 days on average.
These participants also stated that they had cough, shortness of breath and body aches in the acute phase of their illness than other Covid patients.
One limitation of the study is that participants were not asked to continue reporting their symptoms in the weeks and months after their first illness. But the scientists plan to ask volunteers to do so in future research.
“We want to better capture the long-term symptoms so that we can compare the physiological changes we see with the symptoms the participants actually experience,” said Dr. Radin. “So this is really a preliminary study that opens up many more studies.”
In February, the National Institutes of Health announced that they would be allocating $ 1.15 billion to fund research on long-term Covid over the next four years. The new study highlights the role wearables could play in this research, said Dr. Shepherds: “Combining these types of techniques with other studies on this topic of long-term symptoms could really provide a nice, objective look at how things go on with people.”