A Comparative Analysis of Cardiac Sympathetic and Parasympathetic Activity in Sleep Using Linear and Nonlinear Indices.
Level 4 - case-series / case-control
Small observational physiological study in healthy volunteers
PubMed 41336266 · doi:10.1109/EMBC58623.2025.11253331
What was done
In 18 healthy individuals undergoing full-night sleep recording, researchers analyzed cardiac sympathetic (SA) and parasympathetic activity (PA) during wakefulness versus sleep. Autonomic measures were computed from heart rate variability (HRV) series using linear and nonlinear methods: sympathetic activity index (SAI), parasympathetic activity index (PAI), and their ratio derived from a Laguerre expansion of Wiener-Volterra autoregressive kernels; standard frequency-domain metrics (low-frequency power, high-frequency power, and LF/HF ratio); and detrended fluctuation analysis scaling exponents.
What was found
The abstract reports significant differences in autonomic indices between wakefulness and sleep, but provides no numerical values, effect sizes, confidence intervals, or exact p-values. SAI variability was reported to be higher during wakefulness, PAI increased during sleep, and nonlinear analysis showed higher sympathetic short-scaling exponents during sleep compared to wakefulness.
Why it matters
Combining nonlinear HRV complexity measures with traditional autonomic indices provides a more detailed framework for characterizing autonomic nervous system shifts across the sleep-wake cycle.
Limits
The sample size is very small (n = 18) and restricted to healthy individuals, limiting generalizability. Specific sleep stages (such as NREM versus REM) were not differentiated in the primary reported summary, and the abstract omits quantitative point estimates and dispersion metrics.
Cited by
- supports During sleep, heart rate variability increases, parasympathetic tone increases, and the sympathetic nervous system becomes quiet.