What is melatonin?
Melatonin is a hormone produced by the brain while the body is in sleep mode, which regulates the body in its stages of sleep. The body is known to have five stages of sleep which are stages 1, 2, 3, 4, and rapid eye movement (REM). Note that in some other writeups, there are only four stages of sleep, which is because the third and fourth stage were combined into one. But, for the purpose of this study that has looked into melatonin and sleep apnea, there are five stages.