Which stage of sleep accounts for the greatest portion of the epoch?

Stage 2 NREM sleep accounts for the greatest portion of the sleep cycle during a typical night. This stage is characterized by specific EEG patterns, such as sleep spindles and K-complexes, which indicate that the brain is transitioning into deeper sleep while still maintaining some degree of awareness. During sleep, individuals experience several cycles that generally last around 90 minutes each, and as the night progresses, the duration of Stage 2 increases, comprising approximately 45-55% of total sleep time.

While other stages of sleep, such as Stage 1, Stage 3, and REM, play important roles in the overall sleep architecture, they do not occupy as much time as Stage 2. Stage 1 is a light sleep often serving as a transition between wakefulness and deeper sleep. Stage 3, also known as deep sleep, is critical for restorative functions but occurs for a shorter duration. REM sleep, while vital for cognitive restoration and memory processing, tends to appear later in the sleep cycle and for shorter periods compared to the dominant Stage 2.