Dr. Sarah Mitchell
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The Science of Baby Sleep: Understanding and Improving Your Child's Sleep Habits

It’s important to understand WHY you’re implementing the actions you’re taking and understanding baby sleep so you can be a great sleep detective.  That’s why we’re talking about sleep science and what drives your baby to sleep. 

Sleep Science, what does that even mean?

Don’t kids just know how to sleep on their own? Well yes and no. Our drive to sleep is physiological, we need sleep, we can’t live without it. So yes, we sleep naturally but the WAY in which we sleep is learned.  In this blog we’ll talk about sleep science and sleep behavior. 

While the drive to sleep is physiological, the way that we sleep is a learned habit. This means your body craves sleep.  It needs it to sustain life. However, the way we sleep is a learned habit.  Think about yourself.  If I told you tonight you can’t sleep in your favorite position and I’m taking away your pillow.  That would be uncomfortable for you.  You would toss and turn until you learned a new way to fall asleep.  

Learned habits are the way your baby has been conditioned and at some point prefers to fall asleep.  This can look like a baby that is older than 4 months who will only feed to sleep, an 18 month old who needs a bottle of milk to fall asleep and then again in the night.  A two year old who needs a parent to lie beside them to fall asleep and then continues to wake up in the night… expecting the same approach. But not all babies and toddlers need these same approaches, so how does this sleep thing work?  

As parents, most of us inadvertently teach our little ones unsustainable sleep associations in the newborn stage.  Is there anything wrong with nursing your baby to sleep?  Absolutely not, but for many families the frequent night wakings as the child ages become unsustainable.  Sleep is a learned habit and you can absolutely work on gentle newborn sleep shaping in the 4 to 10 week range to help set up sustainable habits and avoid having to do “sleep training.” Sleep training should be called sleep re-training since most of us unknowingly teach our little ones a certain way to fall asleep.  In this 2022 study of over 2000 parents they found that 64% of parents did some sort of sleep training.   What’s interesting about this study is that parents used modified extinction and full on extinction techniques.  In my book, The Helping Babies Sleep Method we refer to “modified extinction” as “controlled crying.”  In this study the average age of implementation was 5.3 months but some babies were as young as 3 months.  No parents reported any adverse effect on mood, physiology or attachment. 

You may have heard of putting your baby down “drowsy but awake”  in The Helping Babies Sleep Method we believe in putting the baby down “calm but awake.” What’s the big difference? If you are making your child drowsy in your arms and then putting them down, you are creating the association of being held and sleep happens in arms.  This can be an association that can be hard to maintain as your baby gets older, more aware of their surroundings and then starts to reject being put down.   This is when you see parents having to repeat their rocking then putting down over and over again to get their little one to sleep. By practicing “calm but awake” you teach that the onset of sleep happens in the space that they are going to be sleeping long term. 

The 3 Systems That Drive Sleep 

The Circadian Rhythm

The first system is circadian rhythm.  The sun comes up, light hits the eye and this tells your brain it’s time to be awake.  The sun goes down and that allows the release of melatonin from the pineal gland.  Melatonin release signals the brain that it’s time to sleep. Research shows that babies get melatonin from breast milk and do not start producing it themselves until 10-12 weeks of age. Research also shows that babies do not fully develop their circadian rhythm until around 6 months of age. This is also when we will start to see a more common napping pattern.

Homeostatic Pressure

The second system is the homeostatic system or sleep pressure. As your body burns through fuel you break down the molecule ATP. With this breakdown you get energy and a byproduct, the protein adenosine.  Adenosine builds up and hits a threshold which then signals to the brain that it is time to sleep. This starts a chemical cascade in the brain that is highly complex but initiates sleep.  The rate of breakdown of ATP is related to a human’s metabolism.  Babies are growing exponentially and thus they burn through fuel more quickly and the build up of adenosine, or sleep pressure, happens faster than in adults, and hence the need to nap.  Napping serves to avoid overstimulation and allow for rest.  The amount of time it takes for the buildup to occur is commonly referred to as “awake windows.”  Wake windows are observational measures of time that note the ideal time to put down for naps and bedtime.  For example, a 6 month old can comfortably stay awake about 2.5 hours between naps.  Putting a baby down before that window or later can make it harder for them to settle.  This is why wake windows are so important. 

The Emotional Cognitive System 

The third system is the emotional cognitive system. If you are distracted by something it can be harder to fall asleep, or stay asleep. This could be a wet diaper, being too cold/hot, or visual distractions. As adults this happens to us too. There may be times where it is harder to sleep if we have big life events coming up. In adults we have little bouts of insomnia, but in babies we call this a sleep regression. Every time you hear sleep regression, think of growth and distraction. This could be emotionally or physically, such as growing teeth, which could be distracting them from falling asleep. It’s important to note that this doesn’t mean that they can’t sleep, but they may have a harder time falling asleep. 

In summary, the three systems that govern your sleep are: circadian rhythm, homeostatic system or sleep pressure, and the emotional cognitive system. 

If you are struggling with sleep Dr. Sarah has a step-by-step approach to help you form 0-24 months to help you navigate sleep science and sleep behavior.  Check out Amazon or Audible for The Helping Babies Sleep Method: The Art and Science of Teaching Your Baby to Sleep.

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