Anatomy of a Sleep Cycle

Summary

One sleep cycle averages ~90 min and rotates through four stages. REM lengthens with each successive cycle.

Takeaway

Most deep sleep happens in cycles 1–2; most REM in cycles 4–5. Cutting sleep short cuts REM disproportionately.

Citations · 1

1. [01]
   Carskadon MA, Dement WC (2017). Normal human sleep: An overview. Principles and Practice of Sleep Medicine, 6th ed.. doi:10.1016/B978-0-323-24288-2.00002-7
   Source