Assessing the Impact of Sleep Deprivation on Autonomic Nervous System Regulation and Heart Rate Variability in Young Adults

Project Abstract

Sleep deprivation is a pervasive challenge among young adults, with potential consequences for autonomic nervous system (ANS) balance and heart rate variability (HRV) that may influence cognitive performance, mood, and safety. This study investigates how acute and chronic sleep restriction modulates sympathetic and parasympathetic activity, as reflected by time-domain, frequency-domain, and nonlinear HRV metrics, and explores associated physiological and behavioral outcomes in a sample of healthy university students aged 18–25. A mixed-methods design combines a controlled laboratory protocol with real-world sleep monitoring over two weeks. In the laboratory phase, participants undergo baseline sleep (9 hours time in bed) followed by two experimental conditions unilateral sleep restriction (4 hours in bed for three consecutive nights) and partial sleep rebound (4 hours for two nights followed by baseline). Continuous electrocardiogram (ECG) data are collected to derive HRV indices, including SDNN, RMSSD, pNN50, LF/HF ratio, and nonlinear measures such as approximate entropy and sample entropy. Concurrent salivary cortisol and catecholamine assays assess neuroendocrine stress responses, while pupillometry and reaction time tasks quantify cognitive vigilance. In the home phase, actigraphy and sleep diaries supplement objective and subjective sleep quality data, enabling ecological validity assessments. The study tests the hypothesis that sleep restriction induces a shift toward sympathetic dominance, manifested as reduced HRV, elevated resting heart rate, and heightened cortisol, with corresponding decrements in executive function, sustained attention, and mood. Multilevel modeling accounts for within-subject correlations across conditions and time points. Mediation analyses examine whether HRV changes mediate the relationship between sleep loss and cognitive performance, and moderation analyses consider sex, body mass index, caffeine intake, and chronotype as potential amplifiers or buffers. The anticipated results are a reduction in overall HRV with larger decreases in parasympathetic indices (RMSSD, pNN50) and relative LF power elevation under sleep restriction, accompanied by increased sympathetic markers and decreased entropy measures, signaling reduced autonomic complexity. These physiological shifts are expected to parallel slower reaction times, greater variability in attention lapses, and worsened subjective sleepiness and mood. The study aims to establish dose–response relationships between minutes of sleep loss and autonomic disruption, delineate recovery trajectories after restriction, and identify individual differences that predict resilience or vulnerability. Ethical considerations include safeguarding participant well-being during sleep restriction and ensuring informed consent with the option to withdraw. The findings will contribute to a mechanistic understanding of how insufficient sleep perturbs autonomic regulation in young adults and inform interventions targeting HRV enhancement, stress management, and safety-critical performance in academic and occupational settings. Practical implications span wearable-based monitoring for early detection of autonomic imbalance, sleep hygiene education, and policy recommendations to mitigate sleep loss consequences in high-demand environments.

Project Overview

What This Project Is About

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This project looks at how not getting enough sleep affects the body's automatic control systems, especially heart rate patterns. It asks whether sleep loss changes how the body uses signals from nerves that regulate stress, digestion, and heartbeat, and how this shows up in heart rate variability (HRV), a simple measure of how much your heart rate varies over time. The goal is to understand if sleep deprivation disrupts normal bodily regulation in young adults and what that might mean for health and daily performance.

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The Problem It Addresses

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Many young adults experience irregular sleep due to study, work, or social life. This can alter autonomic nervous system balance and HRV, but the extent and practical consequences are not fully clear. The project investigates the gap between sleep quality and measurable physiological responses, aiming to clarify risk indicators for fatigue, impaired cognition, or cardiovascular stress.

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Objectives of the Project

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1. Assess changes in HRV after a period of sleep deprivation compared to normal sleep.
2. Identify which autonomic markers are most sensitive to short-term sleep loss.
3. Explore relationships between subjective sleepiness and physiological signals.
4. Evaluate potential compensatory mechanisms in young adults.

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What You Will Do Step by Step

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1) Review basic concepts of sleep, autonomic nervous system, and HRV. 2) Recruit healthy young adult volunteers and obtain consent. 3) Collect baseline night of regular sleep data and a subsequent night with restricted sleep. 4) Record heart rate data and compute HRV indices. 5) Collect subjective sleepiness and mood measures. 6) Analyze changes in HRV between sleep conditions. 7) Correlate HRV changes with sleepiness scores. 8) Discuss practical implications and limitations.

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Expected Outcome

We expect to find reduced HRV after sleep deprivation, indicating heightened sympathetic activity or reduced parasympathetic control. The study should identify which HRV metrics most reliably reflect sleep loss and how these changes relate to perceived alertness. The findings could inform guidelines for students and workers about the physiological costs of poor sleep and help in designing interventions to reduce health risks.