Melatonin is a hormone in your body that plays a role in sleep. The production and release of melatonin in the brain is connected to time of day, increasing when it's dark and decreasing when it's light. Melatonin production declines with age. People commonly use melatonin for sleep disorders, such as insomnia and jet lag. Research suggests that melatonin might reduce evening confusion and restlessness in people with Alzheimer's disease, but it doesn't seem to improve cognition. Your body likely