The Vital Role of Sleep in Human Health: Stages, Mechanisms and the Consequences of Sleep Disruption

Purpose: To summarize the biological significance of sleep, its regulatory mechanisms, and the health impacts of insufficient or disrupted sleep. Methods: This review synthesizes current scientific understanding of sleep physiology, emphasizing the coordinated roles of neural, metabolic, hormonal, and immune systems, and outlining the distinct functions of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages. Results: Sleep is an active, tightly regulated process essential for maintaining physical and cognitive health. NREM sleep supports tissue repair, growth hormone release, metabolic restoration, and declarative memory consolidation, whereas REM sleep underpins emotional regulation, neural plasticity, and procedural learning. Insufficient or disrupted sleep impairs cognition, mood, and alertness, and long-term deprivation contributes to metabolic dysfunction, hormonal imbalance, cardiovascular disease, immune suppression, psychiatric disorders, neurodegeneration, and increased mortality. Conclusions: Sleep is a central pillar of overall health, comparable in importance to diet and exercise. Its wide-ranging physiological influence underscores the need for clinical and public health strategies that promote healthy sleep behaviors and mitigate the adverse effects of sleep disruption.