Sleep Architecture

Sleep architecture is the basic structural organization of our sleep as it cycles through various stages throughout the night. Rather than being a uniform state, normal sleep follows a predictable pattern of brain activity and physiological changes. A full progression through these stages takes 90-120 minutes. Most of us complete 4-6 cycles/night. Architecture also changes across the night: deep N3 sleep more prominent in first half, while REM periods become longer and more frequent in second half. Factors such as age, stress, alcohol, and sleep disorders (apnea) can fragment this architecture, leading to unrefreshing rest even if total sleep time is sufficient. Sleep is divided into two primary types: non-rapid eye movement (NREM) and rapid eye movement (REM).

• Stage N1 (light sleep): Transitional phase between wakefulness and sleep.
• Stage N2 (deeper sleep): Most common stage, where heartrate and temperature drop.
• Stage N3 (deep or slow-wave sleep): Most restorative phase for physical repair.
• REM sleep: Associated with dreaming and memory consolidation, characterized by high-brain activity and muscle paralysis.