Baby Sleep Science and Sleep Training

Last Updated: 
July 24, 2022
 | 
6
 minutes read
Written by
Mandy Treeby
Chief Baby Sleep Consultant
Medically reviewed by
Elissa Gross, DO
Board Certified Pediatrician & Lactation Consultant

Sleep coaching and sleep training work with your baby’s natural, biological processes to help your baby fall asleep faster and stay asleep longer. But do you know what those natural biological processes that help your baby sleep are? Or have you wondered what is the science behind baby sleep or the science behind sleep training?

To help you make sense of baby sleep science and sleep training here’s a brief rundown of the science behind your baby’s sleep and how science-backed sleep coaching and sleep training effectively and safely helps improve your baby's sleep.

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To make it easier for parents to instil healthy sleep habits in their babies, and to guide those interested through different science-backed methods of sleep training, a team of pediatricians and sleep consultants developed the Smart Sleep Coach by Pampers™ app. This easy-to-use baby sleep app provides all the personalized information, guidance, and tools you need to sleep train your baby safely, quickly, and effectively – in whatever way you’re comfortable with.

Baby Wake Windows and Sleepy Cues

First, we want to share the definitions of two sleep coaching terms that dovetail with the science. These will be referenced below and become very important when sleep training.

Wake Window: The amount of time your baby is awake between sleeps.

Sleepy Cues: Physical actions or behaviors exhibited by a tired baby who’s reaching the end of their wake window.

  • Yawning
  • Glazed eyes or avoiding eye contact
  • Rubbing their eyes.
  • Pulling their ears
  • Cranky

Watching for sleep cues is very important when sleep coaching because they tell you a wake window is closing. If your baby stays up much later after showing sleepy cues, their wakeup hormones begin to circulate which can lead to overtiredness.

Circadian Rhythm in Babies

One of the reasons experts recommend you wait until your baby is 4-months-old to begin sleep coaching is because that’s when your baby’s circadian rhythm starts to mature.

The circadian rhythm is our internal clock that regulates our sleep, telling us when to wake and rest, over a 24-hour period. We all have a circadian rhythm – babies, adults, even animals – and it’s largely controlled by daylight.

Newborns and very small babies are still developing this rhythm, which is the science behind why their sleep is very disorganized.

Once their circadian rhythm begins to solidify, between 12 and 16 weeks, you’ll notice your baby forms distinct wake windows and exhibits sleep cues when they are ready to rest.

Sleep coaching works with these natural cues to shape your baby’s sleep, help them

Sleep Hormones in Babies

The circadian rhythm is regulated by hormones that are released and suppressed over the course of a 24-hour cycle. This is what causes your baby’s sleep drive to strengthen the longer they are awake until it’s time for them to sleep again. Sleep coaching using the Smart Sleep Coach app makes it easy to align nap and bedtimes with this natural cycle, so your baby falls asleep faster and stays asleep longer.

Here we define sleep hormones in babies and then explain how they all interact, and how sleep coaching or sleep training can get your baby’s natural hormones in sync.

Adenosine

A “sleep drive hormone,” adenosine starts to release as soon as your baby wakes up. Once the adenosine reaches a certain level, your baby’s body begins producing melatonin, which signals it’s time to sleep.

Fun fact about naps: babies’ and toddlers’ adenosine builds up faster than an older child or adult, which is why they nap so often – to “reset” their sleep tank.

Melatonin

Melatonin is a natural “sleepy” hormone that helps babies, and adults, fall asleep and rest well. As explained above, melatonin is released once adenosine reaches its upper level. When melatonin is triggered, your baby will start to get sleepy, which is when they exhibit sleepy cues.

Cortisol

Cortisol is a “wake up” hormone released after adenosine is depleted. It signals to  the mind and body that it’s time to rise and shine. If you miss your baby’s wake window, your baby produces cortisol to keep them awake, leading to overtiredness.

Daylight and screens also stimulate cortisol production, which is why we recommend blackout curtains for your baby’s sleep space and to limit screen time close to bedtime.

Serotonin

Another “wake up” hormone is serotonin, which is also released when your baby is ready to wake up. As with cortisol, serotonin will also be released if your baby stays up past their wake window. Like cortisol, it’s also influenced by daylight – another reason why blackout curtains are so important when setting up your baby’s sleep space.

A breakdown of how sleep hormones work  

  • When your baby wakes up, they produce the sleep drive hormone adenosine. As adenosine builds up, your baby grows tired. This is called the homeostatic sleep drive.
  • When adenosine reaches a certain level, the sleepy hormone melatonin is released. When melatonin is released, it leads to drowsiness and sleepy cues. This is your golden opportunity to put your baby down to sleep.
  • By putting your baby down to sleep at the end of their natural wake window, you will align with their natural biological rhythm which is the optimal sleep schedule.
  • Once your baby is asleep, the built-up adenosine recedes.  
  • When adenosine hits its lowest level, it activates the production of the wake-up hormones cortisol and serotonin. Daylight can also activate cortisol and serotonin, which is why blackout curtains are so important in your baby’s sleep space.
  • Wake-up hormones cortisol and serotonin will also be released if your baby stays up beyond their wake window, throwing them off sync and leading to overtiredness – that is the last thing you want in a baby.

How Sleep Training Works

Sleep training and sleep coaching with Smart Sleep Coach takes a holistic science-backed approach to fine tune the core baby sleep fundamentals that your baby needs to sleep.

Based on sleep science, an in-sync biological sleep rhythm, optimal sleep environment, consistent routine, and healthy sleep habits can help your baby sleep better.

What helps babies sleep better

  1. Aligned Biological Sleep Rhythm: When you put your baby to sleep right when they’re ready to sleep, they will fall asleep faster and stay asleep longer. By working with your baby’s natural homeostatic cycle, we can align nap and bedtimes to their sleepy waves.
  1. Optimal Sleep Environment: Where your baby sleeps is almost as important as when they sleep. Creating a sleep-inducing environment for every sleep helps deliver positive sleep associations for your baby. Imagine yourself trying to sleep sitting up in a bright room? Baby sleep science proves that it’s much easier to sleep in a dark room. Same with a room set to the ideal temperature.  
  1. Consistent routine: Once your baby starts to recognize patterns, a consistent bedtime routine will signal to your baby that’s time to sleep and make it easier for them to fall asleep.  
  1. Healthy sleep habits: Instilling healthy habits for sleep are important so your baby doesn’t rely on extra parental support to fall asleep independently. For example, once your baby starts to recognize patterns, they may start to rely on being pat, rocked, or fed to fall asleep. If your baby has a sleep association that is starting to affect sleep, they may just need a little help to develop their independent sleep skills.

Many methods of sleep training can encourage positive sleep habits in your baby, while still allowing you to comfort and feed your baby at night. Smart Sleep Coach can recommend gentle sleep training methods that limit crying.

Sleep Cycles in Babies

Now that we’ve discussed the internal and biological functions behind baby sleep science, let’s take a deeper dive into what’s happening inside your baby’s mind while they sleep.

Types of sleep

You may have heard of REM sleep – “Rapid Eye Movement” sleep, but there’s also something called NREM sleep – non-REM sleep.

These two types of sleep work in tandem to help your baby rest and grow.

  • NREM sleep is a deep, restorative sleep that helps write to long-term memory
  • REM is a more active sleep that helps build learning and cognitive skills.

While your baby experiences both during a nighttime cycle, these sleeps’ concentrations or intensities are different at different times of day: There's more NREM sleep from 7pm-midnight and more REM from midnight on. That’s why early bedtimes matter - you want to ensure your baby is getting both types of sleep, REM and NREM.

NREM sleep appears earlier in the sleep cycle, which is why naps are also important.

Example ideal night of sleep for infants  

  1. Stage One: The first stage of baby sleep is a transitionary period of non-REM sleep that’s lighter. During this stage your baby has just fallen asleep – maybe even still opening their eyes a bit – and it’s easier to wake them.
  1. Stage Two: The second stage of sleep is slightly deeper though still light REM sleep during which your baby is easily awoken.
  1. Stage Three: The third stage of sleep is still REM sleep, but it’s deeper than the previous two sleep stages. During stage three of sleep your baby is harder to wake and often motionless.
  1. Stage Four: The fourth baby sleep stage is non-REM sleep – when your baby is dreaming and possibly moving their arms, legs, or face. This stage usually happens in the first few hours of nighttime sleep before your baby returns to the earlier stages, which is why your baby may wake up earlier than usual from time to time. It’s rarer that your baby will reach stage 4 during a nap.

Final Thoughts

Now that you understand how baby science may affect sleep training, download the Smart Sleep Coach by Pampers™ to get step by step sleep coaching support.  

In addition to bite-sized articles explaining even more about your baby’s sleep, the sleep tracking feature automatically updates your baby’s sleep schedule and its exclusive algorithm customizes sleep coaching approaches based on your baby’s unique sleep habits – all so your baby can sleep well today for a healthier, better rested tomorrow.

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Studies show new parents can lose as much as two hours of sleep every night after their baby comes!

“Thanks to the Smart Sleep Schedule, I’ve been able to follow my baby’s natural rhythm, and stick to the wake windows. This makes a huge difference in her ability to nap longer.”

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Thanks to the Smart Sleep Schedule, I’ve been able to follow my baby’s natural rhythm, and stick to the wake windows. This makes a huge difference in her ability to nap longer.

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How We Wrote This Article

The information in this article is based on the expert advice found in trusted medical and government sources, such as the American Academy of Pediatrics and the American College of Obstetricians and Gynecologists. You can find a full list of sources used for this article below. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.

Sources

Cleveland Clinic, “When and How To Sleep Train Your Baby”

National Heart, Lung, and Blood Institute, “How Sleep Works: Your Sleep/Wake Cycle”

National Institute of Neurological Disorders and Stroke, “Brain Basics: Understanding Sleep”

Pediatrics, “Five-Year Follow-up of Harms and Benefits of Behavioral Infant Sleep Intervention: Randomized Trial”

Sleep Foundation.org, “Circadian Rhythm”  

Yale School of Medicine, “Good Sleep Recipe

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