Sleep is an active neurobiological state essential for synaptic homeostasis, memory consolidation, glymphatic brain waste clearance, and endocrine regulation. Chronic sleep restriction (< 7 hours/night) or circadian misalignment directly attenuates peripheral insulin sensitivity, impairs leptin signaling, elevates evening cortisol, and increases sympathetic vascular tone.
Glymphatic System Clearance During Slow-Wave Sleep
During stage N3 deep slow-wave sleep, interstitial space within the brain parenchyma expands by approximately 60%, driven by astrocytic aquaporin-4 (AQP4) water channels. This facilitates convective cerebrospinal fluid-interstitial fluid exchange, clearing neurotoxic metabolic byproducts including amyloid-beta and hyperphosphorylated tau proteins.