What Are The 5 Stages Of Sleep?

Updated February 18th, 2019

Ever wonder why at times you wake up feeling refreshed while at other times you wake up still longing for a few minutes more, despite sleeping for relatively the same amount of time? Could it be that you’re roused from a certain part or stage of sleep? There are five known stages in the sleep cycle. What are the 5 stages of sleep? And since there are stages, what is the deepest stage of sleep? How long is each sleep stage? What happens during each sleep stage?

Before we get to the stages of the sleep cycle, we first, identify the two types of sleep. NREM and REM. NREM stands for Non-Rapid Eye Movement while REM stands for Rapid Eye Movement sleep. These are distinguished by the rapid eye movement a sleeper makes while sleeping. REM sleep is where dreams occur where we either live in a fantasy world or exist in a world similar to ours, acting out moments of our past or future. Our eyes move rapidly under the closed eyelids as if actually seeing the dream world, hence the term. NREM sleep can be divided into four stages where the last stage is REM sleep. Below are the 5 stages of sleep describing what happens during each sleep stage.

Other sources state that there are only four stages of sleep. So are there 4 or 5 stages of sleep? Both are true but many cite the simplified version of combining stage 3 and 4. So the four stages of the sleep cycle can be summarized as very light sleep, light sleep, deep sleep and REM sleep.

But humans do not experience the 4 or 5 stages of sleep in one go during a sleep session. Each sleep cycle lasts between 90 to 120 minutes. That’s about four cycles for a normal 8-hour period. These sleep cycles don’t tend to be sequential either nor are they completed all the time. There are times that persons only sleep at stages one to two, rinse and repeat and only manage to reach stage 3 and REM into the deep hours of the night.

So although a person gets to sleep 8 hours a night regularly, waking up may not be the same everyday as many factors can affect or disrupt the normal sleep cycle and the amount of deep sleep (stage 3 and 4) the human body requires. Thus there are days when a person feels exhausted despite sleeping for 8 hours or feel refreshed after sleeping for 6 or 7.

The fact that we can’t make up our minds on how many stages of sleep there are or whether or not to classify REM sleep as part of the sleep cycle means that there are parts or this normal but essential human activity that remain a mystery. AT this stage however, we understand enough that as adults, obtaining the right amount of sleep is important to heal the body and restore its strength in preparation for the next day.

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