How does melatonin affect sleep?

Melatonin plays a critical role in regulating the body's circadian rhythm, commonly known as the internal sleep-wake clock. This hormone, produced by the pineal gland in response to darkness, signals to the body that it is time to prepare for sleep. By promoting the onset of sleep and helping to stabilize sleep patterns, melatonin can align the body's biological clock with the day-night cycle, thereby facilitating a regular sleep schedule.

Understanding the impact of melatonin on the sleep-wake cycle helps to clarify why it is vital for sleep regulation. It can aid in sleep onset and maintain the structure of sleep throughout the night, making it an essential factor in achieving restful and restorative sleep. Other options do not accurately reflect the primary role of melatonin in sleep physiology. For example, increasing heart rate during sleep contradicts its calming effects; enhancing REM sleep duration is not directly attributed to melatonin; and decreasing sleep efficiency runs counter to the primary purpose of melatonin in promoting better sleep quality.