Although most people who have COVID-19 recover within a few weeks of becoming ill, many continue to experience symptoms for several weeks or even months after recovering. The most common long-term effects are fatigue, “brain fog,” and loss of smell or taste. A recent study using data from wearable devices found that people who have COVID-19 often experience resting heart rate irregularities long after recovery.

Wearable health monitoring devices – often simply called “wearables” – are electronic instruments that patients or consumers can wear to monitor their health, fitness, activity, or sleep. Wearables can transmit information to a physician or to the user in real time, allowing the wearer to actively participate in monitoring and maintaining their own health. Examples of wearables include smartwatches, activity trackers, and sleep monitors. Data from wearable devices may help identify people who have COVID-19.

The study investigators drew on data collected from DETECT, an app-based study of people who routinely use a smartwatch or other wearable device. The goal of DETECT is to ascertain whether changes in heart rate, activity levels (measured via step count), and sleep can identify early signs of viral illnesses, including COVID-19. They reviewed data from 875 people who developed symptoms of an acute respiratory illness and were tested for COVID-19. Of these, 234 tested positive, and 641 tested negative. They calculated deviations in the participants' baseline heart rate by subtracting their average baseline heart rate from their daily heart rate. They grouped participants based on how many beats per minute that their heart rate deviated from baseline (less than one, one to five, or more than five beats) over a period of 28 to 56 days after developing symptoms.

The data revealed that participants who tested positive for COVID-19 took longer to return to their baseline resting heart rate, activity levels, and sleep quantity than those who did not. They tended to experience a brief period early in the course of their illness during which their heart rate was slower than normal (bradycardia), followed by a heart rate that was faster than normal (tachycardia). Their tachycardia did not resolve until approximately 79 days after initially developing symptoms. About 13 percent of the COVID-19-positive participants experienced an increase in heart rate of more than five beats per minute that persisted more than 133 days. These participants were more likely to have reported cough, body aches, and shortness of breath than those who experienced lesser deviations (less than one beat per minute) from their baseline resting heart rate. Participants' sleep quantity returned to baseline levels about 24 days after developing symptoms, and their activity levels returned to baseline levels after about 32 days.

These findings indicate that COVID-19 elicits a wide range of long-term health effects. The authors of the study posited that these effects reflect autonomic nervous system dysfunction or ongoing inflammation, but further study in larger groups is necessary to fully understand the effects of COVID-19 illness. Learn more about how scientists are using wearable devices to diagnose COVID-19 in this episode featuring Dr. Michael Snyder.

• Link to full study.