Physiology, Sleep Stages

During sleep, our body cycles through 4 different stages consisting of both rapid-eye-movement (REM) and non-rapid eye movement (NREM) sleep. The body usually cycles through these stages on average 4 to 6 times, averaging 90 minutes in each stage. As the night progresses, fewer NREM stages occur, and the duration of REM sleep episodes increases. This article will discuss the progression of the sleep stages and the unique features of each.