A complete sleep cycle takes roughly 90 to 110 minutes.
Understanding the duration of a sleep cycle helps shed light on the structure of a typical night's rest. Sleep doesn't occur as a single block but is instead divided into several cycles that repeat throughout the night. Each cycle consists of different stages, moving between non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.
What Happens During a Sleep Cycle?
According to Physiology, Sleep Stages - StatPearls - NCBI Bookshelf, a typical night's sleep consists of 4 to 5 sleep cycles. The stages generally progress in a specific order within each cycle:
- N1 (Stage 1 NREM): The transition from wakefulness to sleep. It's often characterized by slow eye movements and is relatively brief.
- N2 (Stage 2 NREM): A deeper stage where body temperature drops, heart rate slows, and eye movements stop. This stage accounts for the majority of NREM sleep.
- N3 (Stage 3 NREM): Also known as deep or slow-wave sleep. This is the most restorative stage, characterized by delta waves.
- REM (Rapid Eye Movement): This stage is marked by rapid eye movements, increased brain activity, muscle paralysis, and vivid dreaming.
The progression typically follows the order: N1, N2, N3, N2, and then REM.
Key Facts About Sleep Cycles (Based on Reference)
Here are some key points about sleep cycles as mentioned in the provided reference:
- A complete sleep cycle lasts approximately 90 to 110 minutes.
- A typical night involves 4 to 5 such cycles.
- Approximately 75% of sleep is spent in the NREM stages (N1, N2, N3).
- The majority of this NREM time is spent in the N2 stage.
This cyclical pattern ensures that the brain and body receive the necessary rest and processing time across the different stages of sleep throughout the night.
