Understanding Baby Sleep Cycles

One of the best ways of understanding baby sleep cycles is by being cognizant of how it works..  When I became aware of these cycles it was a game changer.  I now had some good tools to help parents understand what their baby needed and make it possible for babies to go to sleep more easily.

understanding baby sleep cycles

All people, both big and little, have one thing in common. We all share the BRAC (Basic Rest and Activity Cycle). It triggers sleeping and waking in all of us. And we can use knowledge about the BRAC to figure out why babies wake so often during the night and how babies sleep.

The BRAC is a programmed inner clock that drives adult, child, and infant brain activity patterns and other physiological functions in a predictable and repetitive fashion over time. These clocks alternate periods of rest (not necessarily sleep) with periods of activity. The human BRAC is a 90-minute cycle. In the daytime, the BRAC dictates 90-minute cycles of alertness, followed by a dip and then another alert period. The rise and fall of the daytime cycle consists of bright alertness, quiet focus, and daydreaming. At the end of this 90-minute cycle, we have a mild dip in attention, and then we rev up for another 90-minute cycle. At night, we sleep in 90-minute cycles of going down into sleep, then deep sleep, then rising to lighter sleep when we dream, then a moment when we either wake up (and remember it) or we just drift back down into another 90-minute cycle.

During sleep, when adults and children ride this wave of deep and then light sleep, we often don’t do anything, or we may turn over, adjust the covers, and look at the clock, then fade back down into another 90 minutes of sleep. Babies, however, do not know how to do this. Babies are born knowing how to sleep but not knowing how to go to sleep and how to stay asleep.

We have to help the baby get to sleep because the BRAC does not cause a baby to automatically go to sleep! Until a baby is about 4 1/2 months old, her brain will not be developed enough for her to get herself to sleep or to stay asleep throughout the deep and light cycles of sleep. When she was a newborn, and until about 4 1/2  months old, she needed your help to get to sleep and to stay asleep until her sleep needs were met. I’m sure you remember the swaddling, rocking, shushing, swaying, soothing, nursing, whatever it took to help her. Now that she is older, she can learn how to ride these sleep waves without needing your help to transition from the end of one cycle into the beginning of the next one.

A baby sleep cycle goes from drowsy to light sleep, down into very deep sleep, then begins to get lighter and in a young baby, sleep becomes so light that she wakes. But she has not slept enough yet. She probably will wake up crying. She does not need to eat. She does not need to play. She doesn’t even need her diaper changed. She needs to go back into deeper sleep again, and cycle through these short sleeps until she gets her full night of rest.  This is the importance of understanding baby sleep cycles.

Until now, you have been facilitating this cycle-changing, but it’s time for her to learn to self-soothe between these cycles. Until now, you have been helping your untrained sleeper to go back down after each waking, otherwise she gets back to fully alert and will spend the next 90-minute cycle crying unless you can do something to get her back to sleep. Understanding baby sleep cycles will enable you to be mindful of how baby sleeps and her waking patterns so you can identify the optimal times that will allow her to sleep or go back to sleep.  As she gets older she will learns to self soothe and begin to string together several sleep cycles of 3 hours, or 4½ hours, or 6 hours till she can eventually sleep through the night.


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