Yes, humans have sleep cycles.
A typical night's sleep consists of 4 to 5 sleep cycles, each lasting roughly 90 to 110 minutes. These cycles involve a progression through different sleep stages.
Stages of a Sleep Cycle
The general order of sleep stages within a cycle is:
- N1 (Non-Rapid Eye Movement stage 1)
- N2 (Non-Rapid Eye Movement stage 2)
- N3 (Non-Rapid Eye Movement stage 3)
- N2 (Returns to Non-Rapid Eye Movement stage 2)
- REM (Rapid Eye Movement)
Approximately 75% of sleep is spent in the NREM stages, with the majority occurring in the N2 stage.
These cycles repeat throughout the night, although the duration of each stage can vary, especially the REM stage, which tends to lengthen as the night progresses.
