A model characterizing the coupling between slow-wave activity, instantaneous heart rate and heart rate variability during sleep

The cyclical and progressively decreasing dynamics of electroencephalogram (EEG) based slow-wave activity (SWA) during sleep reflects the homeostatic component of sleep-wake regulation. The dynamic changes of heart rate (HR) and heart rate variability (HRV) indices during sleep also exhibit quasi-cyclic trends that appear to correlate with SWA. This article proposes a model to characterize the relationship between SWA, HR and HRV in the polar-coordinate (r-O) domain. Polar coordinates are particularly well-suited to model cyclic shapes with simple (linear) equations in the r-O plane. Group-level analyses and individual-level ones of the correlations between the polar-coordinate transformations of SWA and HR reveal R-2 values of 0.99 and 0.95 respectively. Given that, HR and HRV can be estimated in less obtrusive ways compared to EEG. This research offers relevant options to conveniently monitor sleep SWA.

Automated summary

This study examines the relationship between EEG, heart rate, and heart rate variability during sleep, proposing a model to characterize their relationship in the polar-coordinate domain. Group and individual-level analyses demonstrate high correlations between the polar-coordinate transformations of SWA and HR, offering a convenient way to monitor sleep slow-wave activity.