Understanding Sleep Cycles & Stages
Learn how sleep cycles work, the four stages of sleep, and why each stage matters for physical and mental restoration.
The Four Stages of Sleep
Sleep isn't uniform. You cycle through four distinct stages approximately every 90 minutes throughout the night.
Stage 1 (N1): Light Sleep (5-10 minutes)
Transition between wake and sleep. Easily awakened. Muscles relax, heart rate and breathing slow.
Stage 2 (N2): Deeper Light Sleep (20 minutes)
Body temperature drops, heart rate continues slowing. Sleep spindles and K-complexes protect sleep from disruption.
Stage 3 (N3): Deep Sleep / Slow-Wave Sleep (20-40 minutes)
Most restorative stage. Physical restoration, immune function, tissue growth. Very hard to wake. Sleep talking and sleepwalking occur here.
REM Sleep: Rapid Eye Movement (10-60 minutes)
Vivid dreams, memory consolidation, emotional processing. Brain highly active. Body paralyzed (except eyes and breathing muscles).
Sleep Cycle Progression
Early night cycles have more deep sleep (N3), while later cycles have more REM sleep. This is why waking too early robs you of REM-rich sleep, while going to bed very late reduces deep sleep.
A typical night: Cycle 1 (50% deep sleep, 5% REM) → Cycle 2 (30% deep, 15% REM) → Cycles 3-5 (10% deep, 25-30% REM)
Ready to Improve Your Sleep?
Qumfy provides personalized guidance based on evidence-based sleep science and CBT-I techniques.