As Covid-19 infection rates continue their downward spiral across the country thanks to the highly contagious delta form, researchers continue to learn more about the virus' long-term effects. And one such discovery has come thanks to wearable devices like the Fitbit.

In a paper published by the Journal JAMA Network Open, as reported by the New York Times, researchers found that Covid-19-positive individuals had elevated heart rates for weeks to months.

The study consisted of 857 participants, of whom 234 were Covid-positive. The results showed that cobid-positive participants took longer to return their resting heart rate (RHR), sleep, and step count to normal. In about 32.7% of the participants, RHR deviation increased by more than 5 beats per minute and did not return to normal until 133 days later. This group seemed to be the worst affected by the virus, with a higher frequency of coughing, body aches, and shortness of breath.

Dr. Jennifer Radin, the epidemiologist who led the DETECT study, told The New York Times, "Many people infected with cobid will develop autonomic dysfunction and a kind of ongoing inflammation."

This may explain why some people experience neurological symptoms, such as brain fog, even after the primary symptoms have subsided. Other symptoms include shortness of breath, headache, depression, palpitations, and chest pain.

On average, increases in RHR returned to normal 79 days after symptoms first appeared. Steps and sleep volume returned to normal more quickly, 32 and 24 days for most participants, respectively; the CDC calls this Long Covid.

"This rise we are seeing is concerning, and the general trend is that post-Covid patients are showing that their bodies are still under some stress and experiencing some deconditioning," said Dr. David H. Harris, a cardiologist at Memorial Katie Cardiology in Houston, Texas. Dr. Tariq Daya, a cardiologist in the department, said in an interview with Tom's Guide. Dr. Daya was not involved in this study.

Inflammation of the heart due to infection includes pericarditis and myocarditis. The former causes inflammation of the pericardium, the membrane that surrounds the heart, while the latter causes inflammation of the middle layer of the heart wall. Says Dr. Daya, "After Covid administration, we saw an increase in strokes, an increase in blood clots, and an increase in inflammation around the heart."

Much of the detailed data in this story comes from wearable sensor data. Given that one in five Americans claims to own a wearable, the researchers had enough participants to conduct this study. Scientists at the Scripps Research Translational Institute in La Jolla, California, enrolled more than 37,000 people in the study; DETECT (Digital Engagement and Tracking for Early Control and Treatment) participants had to download the MyDataHelps app and share their data via wearable devices such as Fitbit and Apple Watch.

Last October, the same group of researchers published a study in Nature Medicine that found that those who submitted self-reported symptoms along with wearable data were able to more accurately detect cases of Covid-19 than those who analyzed symptoms alone. Not only that, but Mount Sinai researchers found that health care workers wearing an Apple Watch could detect Covid-19 a week before the onset symptoms or positive test.

The trial may be over, but the Scripps researchers plan to conduct another study asking participants to continue reporting symptoms for weeks or months after the first positive test.

Dr. Daya stressed that the best way to avoid heart disease from covid is to be vaccinated, which has proven effective in preventing the worst effects of the virus.