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Sleep Stages Explained
Sleep is not a single uniform state. Throughout the night the body cycles through several sleep stages that support physical recovery, brain function and overall health.
Main Sleep Stages
- Light sleep
- Deep sleep
- REM sleep
These stages repeat in cycles throughout the night and together form a complete sleep cycle.
Light Sleep
Light sleep makes up a large portion of total sleep time. During this stage heart rate and breathing slow down while the body prepares for deeper sleep stages.
Deep Sleep
Deep sleep is essential for physical recovery. During this stage tissues repair, the immune system strengthens and growth hormones are released.
Many restorative processes of the body occur primarily during deep sleep.
REM Sleep
REM sleep plays a crucial role in memory consolidation, emotional processing and brain recovery. Brain activity is high during this phase.
REM stages usually become longer in the later sleep cycles of the night.
Why Sleep Stages Matter
Healthy sleep contains a balanced distribution of all stages. Modern wearables estimate these phases to help interpret sleep quality and recovery.