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Fitness Trackers Reveal Just How Long It Can Take to Truly Recover From COVID-19

9 JULY 2021

Fitbits, smart watches and other wearable devices are helping scientists track the lingering effects of COVID-19 on the human body. 

Using freely volunteered data from hundreds of fitness and health sensors, researchers have now found it takes about two or three months for the body to recover from COVID-19.

 

The physical symptoms identified varied from individual to individual, but they usually included a faster resting heart rate, excess sleep, or reduced physical activity.

A small subset of those who contracted the virus, roughly 14 percent, had it even harder than that. These 'long haulers', as they have become known, showed unusually fast resting heart rates that stuck around for more than four months. 

Their symptoms at the very beginning of the illness were also more severe; this is interesting as previous reports have found many long haulers only experienced mild initial symptoms from COVID-19. 

"Our data suggest that the severity of early symptoms and a larger initial resting-heart-rate response to COVID-19 may be a predictor of how long it takes for individuals to physiologically recover from this virus," says epidemiologist Jennifer Radin from the Scripps Research Translational Institute.  

"In the future, with larger sample sizes and more comprehensive participant-reported outcomes, it will be possible to better understand why some people recover faster or differently than others."   

The researchers believe this is the first time wearable devices have been used to track the course of an infectious illness over the span of several months, and the results suggests COVID-19 is particularly tricky to recover from - at least for those who show symptoms.

 

Compared to fitness data from 641 sick individuals who did not have COVID-19, the 243 volunteers who did have COVID-19 showed changes in their heart rate, sleep and physical activity that stuck around for much longer.

The differences were most obvious for cardiovascular health, which makes sense, as recent evidence has found COVID-19 can have a lasting impact on the heart and lungs, even in young people and after mild cases. 

On average, the current study found a higher resting heart rate is common after COVID-19 and doesn't return to baseline for about two and a half months. 

Step count, on the other hand, typically goes back to normal after about a month; while quantity of sleep usually returns around day 24.

"Wearable sensor data from smartwatches and activity trackers provide a wealth of data about individual baselines, from resting heart rate and sleep patterns to normal daily activity levels," says Radin. 

"This data is giving us new and better ways to measure how the body changes during infection and how it recovers, which is especially important for a new disease like COVID-19 that we're still learning so much about." 

 

The mysteries around long COVID-19 and similar illnesses like myalgic encephalomyelitis or chronic fatigue syndrome (ME/CFS) are myriad, and in many ways that's because patients have historically not been taken seriously.

Oftentimes, it's hard to describe let alone quantify certain symptoms, like fatigue, brain fog, headache, loss of smell or taste, muscle pain, or breathlessness. And yet that doesn't make the symptoms any less real.

Wearable sensors not only complement a growing stream of patient reports, they also offer an evidence-based route for further research.

These nifty devices now sit on the bodies of more than one in five Americans, which translates to a lot of data if individuals agree to share it with researchers.

The study was published in JAMA Network Open