New research published this week in JAMA Network Open is the latest to indicate that some people experience lingering symptoms of COVID-19 months after recovering.

The data comes out of the DETECT (Digital Engagement and Tracking for Early Control and Treatment) study, which collects health data from different wearables – such as Fitbits, Apple Watches, Garmins, Oura Rings or any others that can share data with Google Fit or Apple HealthKit – to understand individual changes associated with viral illness, including COVID-19.

This portion of the study analyzed 875 Fitbit users who reported symptoms of an acute respiratory illness and underwent COVID-19 testing. It compared their wearable data from baseline through illness and back to baseline to see how COVID-19 affected recovery.

TOP-LINE DATA

Individuals with COVID-19 took longer to return to their resting heart rate, sleep and activity baselines than those with symptoms who tested negative. On average, people with COVID-19 experienced lingering physiological effects for two to three months, with some taking much longer to return to normal.

COVID-19-positive participants tended to experience a dip in resting heart rate at the onset of symptoms, followed by a prolonged period of elevated heart rate that lasted an average of 79 days. However, a small subset of participants (13.7%) experienced a higher-than-normal resting heart rate for more than 133 days.

Step count and sleep amount returned to baseline faster than resting heart rate at 32 and 24 days, respectively.

The study also collected symptom data in the early stages of illness and found that COVID-19-positive individuals experienced higher frequencies of cough, body aches and shortness of breath.

The researchers note that only monitoring symptoms at the onset of illness could be a possible limitation of the study, because they couldn’t compare long-term physiological changes with long-term symptoms.

Despite that, the researchers believe that people who have worse symptoms early on and who experience larger disturbances in their heart rate take longer to recover.

METHODS

Out of the 875 individuals in the study, 234 tested positive for COVID-19 and 641 tested negative.

In the positive group, the average age was 45.3 years and the majority (70.9%) identified as female. Similarly, the average age in the negative group was 44.7 years and most (71.1%) were women.

The research was headed by a team from the Scripps Research Translational Institute.

THE LARGER TREND

The DETECT study kicked off last March, with a goal of identifying areas with viral outbreaks such as COVID-19 more quickly and to use person-specific vital signs to create more individualized approaches to healthcare. So far, more than 38,000 people have contributed their data to the study.

Previous findings from the study show that pairing data collected by wearables with self-reported symptoms could improve COVID-19 prediction.

Around the same time the DETECT study launched, UC San Francisco began its TemPredict Study, which uses data from Oura Rings to predict and track COVID-19. Early results from the study indicate that the temperature data collected by the Oura Ring was able to reliably detect the onset of fevers, one of the most common symptoms associated with COVID-19 and the flu.

Fitbit has been a major contributor to COVID-19 research and previously conducted studies to develop an algorithm for early detection of COVID-19 and to predict the severity of illness, symptom prevalence, illness duration and likelihood of hospitalization. It also published data on sleeping habits during the pandemic and recently partnered with Stanford Medicine to study COVID-19 spread among college athletes.