Which of the following best describes hypnogram?

A hypnogram is indeed a visual representation of sleep stages throughout the night. It displays the various stages of sleep, including wakefulness, light sleep, deep sleep, and REM sleep, over time. This graphical representation allows sleep technologists and clinicians to analyze sleep architecture, duration in each sleep stage, and transitions between stages.

Understanding a hypnogram is crucial for assessing the quality of sleep and identifying any sleep disorders. It provides valuable insights into how a patient progresses through the sleep cycle, which is essential information in polysomnography studies.

The other options, although related to sleep and its assessment, do not accurately describe a hypnogram. A questionnaire assessing sleep patterns would gather subjective information from patients, while an assessment of daytime alertness focuses on how sleep affects wakefulness during the day. A measurement of sleep latency refers to how long it takes a person to fall asleep, which is a distinct concept not captured by the hypnogram.