For an average adult, what sleep stage is predominately found in the last third of the night?

For an average adult, what sleep stage is predominately found in the last third of the night?

• A. N2
• B. REM
• C. N3
• D. Wake

Answer: (B)

As the night progresses, sleep architecture shifts toward more REM sleep. Early in the night, deeper non-REM stages (especially N3) dominate the cycles, but REM periods lengthen and occur more frequently in later cycles. By the last third of the night, REM sleep becomes the predominant stage, with several REM periods occurring and contributing the majority of sleep time. REM is characterized by rapid eye movements, an activated EEG pattern, and muscle atonia, and these REM-rich periods increase as morning approaches, making REM the main sleep stage in that final portion.

As the night progresses, sleep architecture shifts toward more REM sleep. Early in the night, deeper non-REM stages (especially N3) dominate the cycles, but REM periods lengthen and occur more frequently in later cycles. By the last third of the night, REM sleep becomes the predominant stage, with several REM periods occurring and contributing the majority of sleep time. REM is characterized by rapid eye movements, an activated EEG pattern, and muscle atonia, and these REM-rich periods increase as morning approaches, making REM the main sleep stage in that final portion.