A studypublished in npj Digital Medicine yesterday used smartwatch data from users during the first 2 years of the pandemic to identify key changes among those who developed long COVID after infections with SARS-CoV-2, the virus that causes COVID-19.
"Data from wearable devices such as smartwatches or fitness trackers, offer a novel approach to understanding the long-term impact of SARS-CoV-2 by providing objective measurements of heart rate, physical activity, step count, and sleep duration," the authors wrote. "These datasets provide a unique opportunity to establish pre-infection health baselines through continuous, non-invasive, and cost-effective measurements."
The study was based on data collected via the Corona Data Donation App (CDA), a voluntary program run in Germany that collected health data via smartwatches during the pandemic. More than 120,000 study participants voluntarily shared daily data from their watches with researchers, who could then track several vital signs in 15-minute intervals before, during, and after a SARS-CoV-2 infection.
Higher resting heart rates
People with COVID-19–positive tests were compared to negative controls, and differences between the groups were assessed prior to and following infections.
Notably, the authors found that people who later had persistent COVID-19 symptoms following acute infections—or long COVID—had higher resting heart rates (RHRs; mean difference, 2.37 beats per minute) and lower daily step counts (mean, 3,030 fewer steps), at least 3 weeks prior to SARS-CoV-2 infection compared to negative controls.
Data from wearable devices such as smartwatches or fitness trackers, offer a novel approach to understanding the long-term impact of SARS-CoV-2.
The higher resting heart rate and lower activity level persisted for up to 2 weeks following COVID infection among those who later developed long COVID.
"Given the known inverse relationship between RHR and physical activity, these patterns suggest that lower physical fitness levels, possibly due to pre-existing conditions, could increase susceptibility to developing long-term symptoms," the authors wrote.
Fatigue, shortness of breath lingered
During active COVID infections, fatigue and shortness of breath were two subjective symptoms reported more frequently in the COVID-19–positive group, and later among those who developed long COVID.
Overall, 2.6% of all SARS-CoV-2–positive people reported prolonged shortness of breath, 10.4% experienced long-lasting fatigue, and 1.8% had both symptoms.
"We found notable differences in the prevalence of fatigue, shortness of breath, and their co-occurrence in SARS-CoV-2 positive and negative individuals. Both symptoms have been reported as typical, persistent symptoms of COVID-19 which are common in individuals with PCC [post-COVID condition]," the authors wrote.
Interestingly, people with long COVID saw a return within several weeks to baseline heart rate, but they still experienced fatigue.
