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NREM Sleep Cycle

Meaning

The NREM Sleep Cycle, or Non-Rapid Eye Movement Sleep Cycle, represents the initial and longest phase of the sleep period, comprising three distinct stages that precede REM sleep and are characterized by a progressive slowing of brain waves and physiological activity. Stage 1 is the transition to sleep, Stage 2 is light sleep, and Stage 3, or slow-wave sleep (SWS), is the deep, restorative phase critical for physical repair, glucose metabolism, and growth hormone secretion. The quality and duration of this cycle are fundamental determinants of physical recovery, immune function, and the efficiency of neuro-metabolic clearance.