What are the stages of sleep?

Sleep architecture refers to the organization and structure of different sleep stages within a complete sleep cycle. These stages can be broadly categorized into two main types: Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep. The sleep cycle repeats throughout the night, with each sleep cycle lasting approximately 90 to 110 minutes.

The two main types of sleep and their associated stages are:

1. Non-Rapid Eye Movement (NREM) Sleep:
Stage 1 (N1): Light sleep occurs as you transition from wakefulness to sleep. It usually lasts several minutes.
Stage 2 (N2): Slightly deeper sleep characterized by sleep spindles and K-complexes. It comprises a significant portion of the total sleep time.
Stage 3 (N3): Deep sleep or slow-wave sleep (SWS), also referred to as “delta sleep,” is characterized by slow and high-amplitude brain waves. This stage is essential for physical restoration and recovery.

2. Rapid Eye Movement (REM) Sleep:
REM Sleep: Dreaming typically occurs during REM sleep, characterized by rapid eye movements, increased brain activity, and vivid dreams. The body experiences muscle atonia, meaning voluntary muscles are temporarily paralyzed to prevent acting out dreams.

The sleep cycle typically progresses from Stage 1 to Stage 2, then into the deeper NREM Stage 3 (SWS), followed by a period of REM sleep. This cycle repeats several times throughout the night. The proportion of time spent in each stage can vary across the night, with a greater amount of REM sleep occurring in the later sleep cycles.

Understanding sleep architecture is crucial for assessing overall sleep quality. Disruptions in sleep architecture, such as frequent awakenings or insufficient time spent in certain stages, can contribute to sleep disorders and impact overall sleep quality. Sleep studies are used to monitor and analyze sleep architecture.