Which of the following is true of a night’s sleep?
Multiple Choice
REM sleep decreases as the night progresses.
Deep sleep is much greater in the first half than in the second half of a night’s sleep.
Individuals normally spend about 20 percent of sleep in light sleep.
Most REM sleep takes place during stage N1 of a night’s sleep.
The Correct Answer and Explanation is:
Correct Answer:
Deep sleep is much greater in the first half than in the second half of a night’s sleep.
Explanation:
A typical night’s sleep follows a predictable structure consisting of multiple sleep cycles, each lasting approximately 90 minutes. These cycles are divided into non-REM (NREM) sleep and REM (rapid eye movement) sleep stages. NREM sleep itself includes three stages: N1 (lightest sleep), N2 (slightly deeper), and N3 (deep or slow-wave sleep).
The correct statement — “Deep sleep is much greater in the first half than in the second half of a night’s sleep” — accurately describes the natural architecture of sleep. In the first half of the night, the body experiences longer periods of N3 (deep sleep). Deep sleep is essential for physical restoration, immune system support, and memory consolidation. As the night progresses, the amount of N3 sleep declines, and the body shifts toward longer periods of REM sleep.
In contrast, REM sleep, associated with vivid dreaming, emotional processing, and brain development, increases in duration in the second half of the night. The first REM period may only last a few minutes, but by early morning, REM phases can last up to 30 minutes or more.
Let’s evaluate the other options:
- “REM sleep decreases as the night progresses” — False. REM sleep actually increases throughout the night, not decreases.
- “Individuals normally spend about 20 percent of sleep in light sleep” — False. Light sleep (mainly N1 and N2) accounts for roughly 50–60% of total sleep time, not just 20%.
- “Most REM sleep takes place during stage N1 of a night’s sleep” — False. REM sleep is a separate stage entirely, distinct from N1. It is not part of the NREM sleep stages.
In summary, deep sleep (N3) dominates early in the night, while REM sleep becomes more frequent and longer in the latter half. This natural balance ensures both physical and mental rejuvenation.