In a normal young adult, which sleep stage is characteristic of 2-5% of total sleep time (TST)?

The percentage of total sleep time (TST) attributed to each sleep stage can vary, but in a normal young adult, non-rapid eye movement stage 1, also known as N1, is typically characterized by making up approximately 2-5% of TST. N1 is the lightest stage of sleep and represents the transition from wakefulness to sleep. During this stage, individuals may experience a reduced level of awareness and can be easily awakened.

Understanding the typical distribution of sleep stages in a healthy adult is crucial for both the diagnosis and treatment of sleep disorders. N2, which is the next stage of non-REM sleep, tends to occupy a more significant portion of TST, while N3, the more restorative deep sleep stage, and REM, known for vivid dreaming, also contribute more substantially to total sleep time compared to N1. Therefore, correctly identifying N1 as the stage that contributes 2-5% of TST is essential in recognizing the patterns of sleep architecture in a normal young adult.