Coupled Heart-rate and physical activity and Circadian Fragmentation in COVID 19

Wearable devices continuously record physiological signals such as heart rate and physical activity, at high temporal resolution creating an opportunity for large-scale health monitoring. Using the Corona Data Donation dataset anchored to PCR test dates, we characterise COVID-19 physiological disruption. We characterise COVID-19 physiological disruption across a cohort design of healthy and test-positive individuals. Our contributions are twofold. First, while existing approaches rely on univariate signals such as resting heart rate for studying infection, we introduce Mahalanobis Distance (MD) to simultaneously capture the coupling between heart rate and physical activity relative to a healthy population baseline. MD reveals that both heart rate and physical activity deviate significantly from healthy norms at COVID-19 onset (or few days prior to onset), with recovery taking approximately two weeks. Next, we measure the 24-hour circadian rhythm strength of these physiological signals using Lomb-Scargle periodograms; a non-parametric frequency-domain measure of 24-hour rhythm strength in the physiological signal. We observe that COVID-19 infection disrupts the dominant 24-hour rhythmic period, shifting power toward shorter ultradian harmonics and indicating fragmentation of the daily activity rhythm. This circadian disruption persists for approximately two weeks before recovery to 24-hour rhythmicity is observed. These two metrics provide complementary signatures of COVID-19 physiological disruption. These suggests their pre-infection values jointly predict severity and recovery trajectory.

Key messages

• MD reveals that both heart rate and physical activity deviate significantly from healthy norms at COVID-19 onset with recovery taking approximately two weeks.

• We observe that COVID-19 infection disrupts the dominant 24-hour rhythmic period, shifting power toward shorter ultradian harmonics and indicating fragmentation of the daily activity rhythm.