Fitbit Stats Show Lingering Physiologic Hit After COVID-19

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People infected with SARS-CoV-2 can experience lingering physiologic effects after they recover, according to early data from an ongoing study that is harnessing the power of Fitbits and other wearable trackers to gauge long-term effects of COVID-19.

“To our knowledge, this is the first study to examine longer duration wearable sensor data. We found a prolonged physiological impact of COVID-19 infection, lasting approximately 2 to 3 months, on average, but with substantial intra-individual variability,” report Jennifer Radin, PhD, MPH, and colleagues with the Scripps Research Translational Institute, San Diego, California.

The study was published online July 7 in JAMA Network Open.

The DETECT study is enrolling adults from all over the United States and is collecting their health data from different wearable devices to better understand changes associated with viral illness, including COVID-19.

The current analysis focuses on a subset of 875 device wearers who reported symptoms of an acute respiratory illness and underwent testing for SARS-CoV-2. A total of 234 individuals tested positive for SARS-CoV-2; 641 were presumed to have other viral infections (COVID-19-negative symptomatic individuals).

The investigators found that among people with COVID-19, it took longer to return to baseline status with respect to resting heart rate (RHR), sleep, and activity compared with those who had symptoms of viral illness but who did not have COVID-19.

“This difference was most marked for RHR, with COVID-19-positive individuals initially experiencing a transient bradycardia followed by a prolonged relative tachycardia that did not return to baseline, on average, until 79 days after symptom onset,” Rabin and colleagues report.

Step count and sleep quantity returned to baseline values sooner than RHR, at 32 days and 24 days, respectively.

Among people with COVID-19, during recovery, trajectories differed with respect to return of RHR to normal in comparison with persons who did not have COVID-19.

The RHR of 32 COVID-19-positive participants (13.7%) remained 5 beats/min greater than their baseline RHR for more than 133 days, on average. During the acute phase of COVID-19, these individuals were more apt to report cough, body ache, and shortness of breath compared with other groups.


The researchers say a limitation of this analysis is that symptom data were collected only during the acute phase of infection, which limits the ability to compare long-term physiologic and behavioral changes with long-term symptoms.

“In the future, with larger sample sizes and more comprehensive participant-reported outcomes, it will be possible to better understand factors associated with inter-individualized variability in COVID-19 recovery,” they conclude.

Earlier data from the DETECT study showed that pairing wearable tracker data with self-reported symptoms can improve COVID-19 prediction.

As previously reported by Medscape Medical News, DETECT investigators found that associating participant-reported symptoms with personal sensor data, such as deviation from normal sleep duration and RHR, resulted in an area under the curve of 0.80 for differentiating between symptomatic individuals who were positive and those who were negative for COVID-19.

Funding for the current study was provided by a grant from the National Center for Advancing Translational Sciences at the National Institutes of Health. The authors have disclosed no relevant financial relationships.

JAMA Netw Open. Published online July 7, 2021. Full text

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