The Science behind baby sleep

It’s bedtime for your baby. You give her a bath, get her all cozy in pjs, all is calm and peaceful. Until it’s time to actually lay her down. Due to her intense protesting, you resort to bouncing and rocking her to sleep. After a few nights like this, you don’t even bother laying her down awake and just go ahead with the bouncing and rocking knowing that nothing else works. You get 45 min of quiet happy sleep and she’s awake again, crying for you to come in and do it all over again. Sound familiar? Even if not exactly, this is an example of a very common night in many homes with little ones. It becomes a vicious cycle of frustration and exhaustion on both the parents/caregivers and the babes.

Here’s the question I get asked all the time: Why won’t my baby sleep through the night? It’s a great question, but a difficult one to answer without understanding the science behind sleep. In this blog I will discuss the affect poor sleep has on your baby’s development, what a circadian rhythm is, and how sleep is not just one continuous block of dreams but rather a rollercoaster of stages.

How Does Sleep (Or Lack Thereof) Affect My Baby’s Development?

While there isn’t a clear answer to why we sleep, scientists have discovered many benefits associated with sleep that are crucial to the proper functioning of our brains and bodies. Sleep is the time where our bodies restore what is lost during the day and when we perform activities to prepare for a new one, including tissue repair, protein synthesis, and the release of the growth hormone. Getting healthy sleep is extremely important to your baby’s proper development and growth.

While it may seem like they are getting all of the sleep they need because you are doing your part in making sure they are rocked, nursed, bounced, etc to sleep every time they wake, they are actually experiencing poor sleep. Think about when you get a poor night’s sleep. You usually characterize this as “I woke up every hour” or “I had so much trouble staying asleep last night”. This is what your baby (and their developing brain and body) is experiencing when they are not able to transition from one sleep cycle to the next without a specific prop.

What Is The Circadian Rhythm and Sleep Pressure?

Our circadian rhythm is essentially our body’s internal clock that controls when it’s time to sleep and when it is time to be awake. Us sleep consultants like to refer to it as our natural sleep/wake cycle. It is mostly driven by light and darkness. When it’s dark your body produces melatonin, the hormone that helps us to fall asleep and stay asleep. On the flip side, when light travels through our eye, we send a signal to our hypothalamus which then signals for our body to suppress melatonin and instead produce cortisol, allowing us to stay awake all day long. However, we are all born with an underdeveloped circadian rhythm, which is why newborns experience day/night confusion. It is not until about 3 months of age that your baby will have a fully developed circadian rhythm, hence why sleep up until this time is often erratic and unpredictable.

Furthermore, there is something else that controls our need for sleep called homeostatic sleep pressure. Sleep pressure is highest in the evening, and lowest in the morning. When pressure is high, falling asleep is easy. However, when it is low it can be very difficult to get your baby to sleep. So, if you have a baby that experiences early morning wake-ups or has trouble falling asleep during the day for naps and seems to protest harder during these times versus at bedtime, his/her sleep pressure is to blame. Getting the timing down is not easy, however it is possible with proper awake periods, schedules, and routines.

What Are The Stages Of Baby and Child Sleep?

There are two types of sleep: REM sleep and Non-REM sleep. When she is born, your baby will only experience these two stages, more commonly known as light sleep and deep sleep. By about 4 months of age, your baby will start cycling through all four stages of sleep, stages 1-4 are Non-REM and stage 5 is REM sleep. Here is a breakdown of each stage:

Stage 1 - Very light sleep. Your baby’s eyes are heavy and start to close. They appear drowsy and start to dose-off.

Stage 2 - Light sleep. Your baby appears to be falling asleep yet can be startled awake very easily. This is why your baby wakes immediately upon laying them down in their crib after being “rocked to sleep” even though they seemingly appear fast asleep.

Stage 3 - Deep sleep. Your baby’s brain waves start to slow as they slip into a deep sleep.

Stage 4 - Deepest sleep. This is where restoration of muscles, tissue repair, immune system building, and all other development related benefits kick in.

Stage 5 - REM sleep. Your baby is now in a light but active state of sleep. REM sleep is where dreaming occurs, so their brains are active but their bodies are still in a paralyzed state.

The completion of all of the stages is considered one sleep cycle. While it is not always consistent, sometimes babies (and adults too) start with stages 1-4 then bounce back to 3, or 2, eventually they get to stage 5. At the completion of stage 5, either your baby wakes up or the cycle starts all over again at stage 1. As the night goes on, REM sleep becomes longer and longer. As adults we remember our dreams most vividly first thing in the morning after we experience our longest REM stage. For babies, because their sleep cycles are much shorter than adults, this means spending more time in a lighter state of sleep as the night progresses, which usually equals more likelihood of waking up frequently throughout the early hours of the morning.

How Do Sleep Cycles Affect My Baby or Child’s Sleep?

This cycle of stages repeats itself over and over again throughout long naps and nighttime sleep. However, if your baby has not yet learned independent sleep, chances are they are likely waking every 1-2 cycles as they transition from REM sleep to light sleep looking for the prop that helped put them to sleep in the first place. You could imagine that you would be pretty confused and frustrated if you were rocked and cuddled to sleep and then woke-up still and alone, not knowing how to fall back to sleep on your own. The need for specific sleep props to transition between sleep cycles often results in frequent, unnecessary night-time wakings and short naps.

This is why teaching your baby independent sleep is so important. Without proper sleep your baby is cranky and has difficulty practicing milestones. When your baby is not well rested, bumps in the road, such as illness and teething, are much more difficult to cope with. Furthermore, it has been shown that poor sleep does not just fix itself on it’s own and can likely continue into later years. By teaching your baby to fall asleep independently, you will eliminate unnecessary night-time wakings and lengthen naps allowing you and your baby more much-needed, development-promoting, consolidated sleep. 

Better Sleep Is Possible

Sleeplessness does not have to be you norm. Schedule a FREE 15 minute assessment call with me to discuss how to get your baby on track to independent sleep using gentle, step-by-step sleep training methods. Head to my contact page to get started.