When you sleep, your body goes through a pattern called the sleep cycle, which repeats about 4 to 6 times each night.

Each cycle takes roughly 80 to 100 minutes.

Sleep stages

  • Stage 1 (N1) — Light sleep: This is the very start of sleep, a light and brief stage where you drift off. Your muscles relax, your heartbeat slows, and your eye movements become slow. It’s easy to wake up during this phase.
  • Stage 2 (N2) — Deeper light sleep: In this stage, your body temperature drops, muscles relax further, and your heartbeat and breathing slow down and become more regular. Brain waves slow, but quick bursts of activity help keep you asleep by blocking out distractions.
  • Stage 3 (N3) — Deep sleep: Also called slow-wave or restorative sleep, this is the deepest sleep stage. Your body repairs tissue, strengthens the immune system, and conserves energy. Waking during this stage is difficult, and it’s crucial for feeling refreshed when you wake up.
  • REM sleep: Usually starting about 90 minutes after falling asleep, REM (rapid eye movement) sleep is when most dreaming happens. Brain activity increases, breathing becomes irregular, and muscles are temporarily “paralyzed” to prevent you from acting out dreams.

Your brain cycles through these stages multiple times, giving your body and mind a chance to rest, heal, and get ready for the next day.

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Narcolepsy is a sleep disorder that disrupts the normal sleep cycle.

It causes sudden, uncontrollable “sleep attacks”, even if you got enough sleep the night before.

People with narcolepsy often feel very sleepy during the day and may suddenly fall asleep at inappropriate times, like during conversations or driving.

Symptoms of narcolepsy that differ from normal sleep cycles include:

  • Daytime sleepiness: Feeling tired all day, even after a full night’s sleep. This is often the first sign to appear, and everyone with narcolepsy will experience it to some degree.
  • Sleep attacks: Falling asleep without warning, which can happen anytime and potentially cause danger.
  • Muscle weakness (cataplexy): Sudden muscle weakness triggered by emotions like stress or excitement, which doesn’t occur in normal sleep. You may or may not have this symptom.
  • Quick entry to dreaming: Falling into REM sleep very quickly, sometimes within minutes of falling asleep.
  • Sleep hallucinations and sleep paralysis: Some people experience dream-like images while awake or are unable to move during sleep transitions, such as falling asleep or waking.
  • REM sleep behavior disorder (RBD): You may experience RBD, which is where your muscles are not “paralyzed” like usual during sleep. This can cause you to move, kick out, or shout while you’re asleep.

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