Difficulty falling asleep at desired time.

• A. NREM Stage III IV
• B. Delayed Onset of Sleep
• C. Fragmented Sleep
• D. Normal Sleep Cycle

Answer: (A)

Difficulty initiating sleep is the issue here. When someone has trouble falling asleep at a desired bedtime, it points to delayed onset of sleep—a circadian timing problem where the body's internal clock is shifted later, making it hard to start sleeping at an conventional or chosen time, even though once asleep the person can wake and sleep relatively normally.

This is distinct from deep sleep stages (NREM Stage III/IV), which describe the quality of sleep once it has begun and occur after sleep has started. Fragmented sleep means multiple awakenings during the night, not trouble initiating sleep. A normal sleep cycle refers to the typical progression of sleep stages across the night, not initiation difficulty.

So the best way to describe difficulty starting sleep at a desired time is delayed onset of sleep.