What happens to REM sleep during a sleep cycle?

During a sleep cycle, REM (Rapid Eye Movement) sleep typically gets longer as the night progresses, while the duration of deep sleep (non-REM sleep) tends to decrease. This phenomenon is an important aspect of how sleep architecture operates.

In earlier sleep cycles, deeper stages of non-REM sleep dominate, which are crucial for physical restoration, memory consolidation, and other restorative processes. As you cycle through sleep stages, the amount of time spent in REM sleep gradually increases with each cycle. This allows for more extended periods of dreaming, as REM is the stage where most vivid dreams occur.

Understanding the relationship between REM sleep and deep sleep can help clarify why individuals often wake up feeling more refreshed and alert after moving through multiple complete cycles of sleep, as the proportion of REM sleep rises toward the end of the night. This shift signifies the brain's transition to processing emotional experiences and integrating memories, making the lengthening of REM periods a critical aspect of a healthy sleep pattern.