What Are Sleep Cycles?
Sleep has to be one of life’s greatest mysteries. We still don’t understand how sleep fully impacts our health or why sleep costs a third of our lifetime. Thanks to the advancements of our knowledge regarding sleep, we now know that a lot more is happening than meets the eye. For example, we used to believe that our brains would remain inactive while we were asleep. It turns out, that couldn’t be any further from the truth.
Our brains are very active (sometimes even more active when you’re asleep than awake!) while we’re fast asleep. So, what does our brain do while we’re snoring zzz’s? It has been found that our brain waves slow down as we enter different stages of sleep or sleep cycles. There are a total of five stages, which make up one sleep cycle. Each sleep cycle should last 90 minutes. Adults should have 5-6 sleep cycles per night. 1 2 3
NREM (non-rapid eye movement) sleep is composed of stages 1-4. Stages 1-2 are considered light sleep. It’s in these stages that we’re easily woken up. By stages 3-4, one has now entered a deep state of sleep. At this point, it’s difficult to be disturbed. During the deeper stages of sleep, our bodies are repairing muscle tissue, bones, and our immune system.
REM (rapid-eye movement) sleep only consists of stage 5. Most dreams occur during this stage. Some speculate that we dream because of the movements the eyes make. However, there is no evidence supporting that statement, which makes sleep even more mysterious. While there’s no evidence for that, it is at stage 5 that our brains become the most active.