Analysis of autonomic cardiovascular control during sleep in healthy adults using heart rate variability and baroreflex sensitivity measures

Project Abstract

Autonomic regulation of cardiovascular function during sleep is a complex, dynamic process influenced by sleep stages, circadian factors, and individual physiological variance. This study investigates how parasympathetic and sympathetic activity modulate heart rate variability (HRV) and baroreflex sensitivity (BRS) in healthy adults across sleep stages, with the aim of delineating normative autonomic patterns and identifying potential latent dysregulations. A cohort of 60 healthy adults aged 20–40 years underwent overnight polysomnography combined with continuous noninvasive cardiovascular monitoring to capture high-fidelity electrocardiography (ECG), systolic blood pressure, and respiration signals. HRV was analyzed in time, frequency, and nonlinear domains during wakefulness and sleep (N1, N2, N3, and REM stages), focusing on indices such as RMSSD, pNN50, LF/HF ratio, and approximate entropy. Baroreflex sensitivity was quantified using sequence methods and transfer function analysis, complemented by spontaneous BRS estimations during temporal windows corresponding to distinct sleep stages. The study also examined autonomic modulation in relation to nocturnal events such as arousals, respiratory pauses, and body position changes. Data preprocessing included artifact rejection, ectopic beat correction, and normalization of HRV metrics to account for age, sex, and baseline fitness. Preliminary results indicate a robust shift toward parasympathetic dominance during NREM sleep, evidenced by increased RMSSD and HF power, alongside reduced LF/HF ratios, while REM sleep exhibits mixed autonomic patterns with intermittent sympathetic surges and reduced baroreflex responsiveness. BRS was highest during deep sleep (N3) and diminished progressively across lighter stages and REM, suggesting stage-dependent buffering of cardiovascular variability. Across the cohort, interindividual variability in HRV and BRS was significantly correlated with baseline vagal tone, resting blood pressure, and BMI, highlighting the influence of intrinsic factors on nocturnal autonomic regulation. A notable finding is the transient reduction in BRS during periodic limb movements and brief arousals, which aligns with transient sympathetic activation and blood pressure fluctuations, underscoring the sensitivity of baroreflex pathways to micro-arousals. The methodological integration of HRV and BRS measures demonstrates complementary insights HRV captures the overall balance of autonomic outflow, while BRS reflects the dynamic regulatory feedback between heart rate and blood pressure, providing a more granular assessment of cardiovascular control during sleep. These findings establish normative ranges for HRV and BRS across sleep stages in healthy adults and illustrate the stability of autonomic control mechanisms under typical nocturnal conditions. The study has implications for early detection of sleep-related autonomic dysfunction, risk stratification for cardiovascular disease, and the development of sleep-preserving interventions that maintain optimal autonomic balance. Limitations include the healthy, young adult sample, which may not generalize to older populations or individuals with comorbidities; future work will extend the cohort to diverse age groups and explore longitudinal changes with habitual sleep patterns and lifestyle factors.

Project Overview

What This Project Is About

---

A plain-language overview of the topic and what the project investigates.

---

---

The Problem It Addresses

---

What problem or gap this project tackles and why it matters to the field or society.

---

---

Objectives of the Project

---

1. Identify how sleep affects the balance between the two branches of the autonomic nervous system.
2. Describe how heart rate variability reflects cardiovascular control during different sleep stages.
3. Explore how baroreflex sensitivity changes across the night in healthy adults.
4. Relate sleep-related autonomic patterns to overall cardiovascular health indicators.

---

---

What You Will Do Step by Step

---

1. Review basic physiology of autonomic control and baroreflexes at a beginner level.
2. Gather or simulate sleep data including heart rate and blood pressure signals.
3. Calculate heart rate variability metrics and assess baroreflex sensitivity.
4. Analyze how these measures vary with sleep stages using simple comparisons.

---

---

Expected Outcome

Expect a clear picture of how autonomic control shifts during sleep in healthy adults and how HRV and baroreflex data relate. The project should yield easy-to-understand findings that can inform further study or basic health awareness.