• Adela

Sleep Cycle Science

Updated: Jun 25


Many of us just think of sleep as an on-or-off situation. You’re either asleep or you’re not. But sleep actually has a number of different stages, and they make up the “sleep cycle,” which we go through several times a night.

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Stages of Sleep


Many of us just think of sleep as an on-or-off situation. You’re either asleep or you’re not. But sleep actually has a number of different stages, and they make up the “sleep cycle,” which we go through several times a night. So here’s the science-y part, told in plain English.


Stage 1 is that initial stage we’re all familiar with where you can just feel yourself drifting off, but don’t really feel like you’ve fallen asleep. Anyone who has ever seen their partner nodding off in front of the TV, told them to go to bed, and gotten the canned response of, “I wasn’t sleeping!” knows exactly what this looks like.


Stage 2, is a lighter stage of non-REM (rapid eye movement) sleep. This is where people tend to realize, once woken up, that they actually were sleeping. For anyone taking a “power nap,” this is as deep as you want to go, or else you’re going to wake up groggy.


Stage 3 deep and regenerative, non-REM sleep. This is where the body starts repairing and rejuvenating the immune system, muscles tissue, energy stores, and sparks growth and development.


Stage 4 deep, REM sleep is where the brain starts to kick in and consolidates information and memories from the day before (long term memory storage). This stage of sleep helps manage emotion like anxiety, depression and pain. It’s also the stage where we do most of our dreaming.


Once we’ve gone through all of the stages, we either wake up or come close to waking up, and then start over again into the next sleep cycle until the alarm goes off. A 1 year old has a sleep cycle that is 45 minutes in length and will lengthens as they age until they have adult sleep cycles that are 90-110 minutes long. It is common for babies to only sleep for 45 minutes if they cannot link to another sleep cycle.


For a deep dive into the health benefits of these sleep stages, check out this killer article with the juicy details: The Power of Sleep: How Much Sleep Is Enough Sleep and Why?

Sleep Regressions


What does this have to do with the dreaded sleep regression all moms fear?


Newborn babies only have two stages of sleep; quiet and active sleep REM (rapid eye movement). When babies reach the 4 month sleep regression, their sleep becomes more adult-like and evolve into 4 stages of sleep. This is means baby spends more time in lighter sleep, thereby creating more chances of night wakings. I go into more detail about this on my post about, "Does the Four Month Sleep Regression Really Exist." For those still stuck in the sleep regression wheel, check out my post on Troubleshooting the 4 month Sleep Regression.


Looking to learn more about setting your baby up for success and giving them healthy sleep habits? Click to download now my FREE 5 step sleep guide and reserve your complimentary 15-minute sleep assessment today to hear how my 1-1 support can help your family.