The Science of Baby and Toddler Sleep

While we sleep, we pass through different stages of sleep, each of them with their own characteristics. In order to get a better understanding of your childʼs sleep behaviour, it is important that you know how sleep works in general. This will also enable you to more easily diagnose the root causes behind your childʼs sleep challenges.

A FEW SLEEP BASICS

• An infantʼs sleep cycle lasts about 50 minutes.

• After this time, there is a brief period of arousal (=transition). This is the moment where many (young) babies wake up easily and have difficulty falling back asleep.

• On average, children have 4 to 6 of these arousals per night, which decrease over time.

• Over time, the sleep cycles gradually lengthen to 90 to 110 minutes, reaching maturity in middle childhood.

• When your child sleeps, they go through two distinct types of sleep, which alternate throughout each sleep cycle: REM-Sleep and Non-REM-Sleep (REM=Rapid Eye Movement).

REM-SLEEP

REM-Sleep is characterized by absent muscle tone and rapid movement of the eyes. During these sleep phases dreaming occurs. Occurs about 70 to 100 minutes a er sleep onset and lasts about 5 minutes.

NON-REM-SLEEP

Knows three distinct stages.

Stage 1: Sleep at the sleep-awake transition (sometimes called “light sleep”) 30 seconds to 5 minutes a er falling (back) asleep.

Stage 2: initiation of “true” sleep.

Stage 3: “deep” sleep or slow wave sleep or delta sleep. Respiration is slowest and most regular during slow-wave sleep.

In the first third of the night, your child spends most of the sleep cycle in non-REM sleep. In the course of the night, REM sleep dominates the sleep cycle more and more. This is the reason why children (and adults) tend to wake up more easily in the early morning hours – their sleep is just lighter than in the beginning of the night AND sleep pressure is lower.

INFANT SLEEP

(0-6 MONTHS) An infant of 0-6 months of age typically goes through three stages of sleep:

1. Active sleep (the precursor to REM)

2. Quiet sleep (an still immature version of non-REM)

3. Indeterminate or transitional sleep which is a mixture of the other two.

Newborns spend 50% of their sleep time in REM sleep. Until they reach the age of 2, the proportion of REM sleep declines to 20-25%.

Check out the below sketch to get an understanding of how your child progresses through the sleep cycles per night:

So now that you know what the architecture of sleep looks like, letʼs take a look at what the actual ingredients are that will make it easier for your child to fall and stay asleep.

CIRCADIAN RHYTHM (THE "INNER CLOCK")

Around the age of 3 or 4 months, your baby will be able to respond to cues such as light/dark and social cues from the environment to indicate periods of wakefulness and sleep. When this is the case, infants will start to sleep more at night and less during the day and may start having a sort of “schedule”. You can help your baby pick up on these cues so that they can easily recognize when it is time for sleep and/or time to be awake.

THIS IS HOW YOU CAN HELP YOUR BABY

• Keep it dark and quiet when it is time to sleep

• Make it light and noisier when it is time to be awake / eat / play

• Start introducing a simple bedtime-routine

• Have a regulated wake-up routine

• Have a stable meal schedule have them play/exercise during the day

Sticking to the above named cues during the entire childhood (or actually throughout life) will help keep the “inner clock” sharp and help the body to find rest when needed.

SLEEP PRESSURE

In order to fall asleep with ease, your child must actually be tired enough. Over the course of the day, sleep pressure builds up more and more as your child slowly drains their energy resources with activities. Naps help recuperate these partially. However, by night time, the pressure to sleep will be high, the body is tired, the mind exhausted. In order to help your child, you should pay attention that they do not sleep too much during the day or until too late in the afernoon (which results in less sleep pressure for the night).

SLEEP LEADS TO MORE SLEEP - OVERTIREDNESS CAN DISRUPT NIGHT SLEEP

There are two major disruptors of night (and day) sleep: being overtired and being overstimulated. Sometimes the one results in the other and vice versa. When your child goes to bed overtired, their body produces the stress hormone adrenaline instead of the sleep hormone melatonin (helping the body to relax and fall asleep).

THIS IS HOW YOU CAN HELP YOUR CHILD

• Stick to age appropriate awake windows.

• Provide a quiet and peaceful environment for naps and night sleep.

• Support the circadian rhythm (see above)

• Keep daily activities rather low than too much (especially for young babies, being exposed to lots of stimuli such as music, strange people holding them etc. can be very stressful)

Now that you have an understanding of how sleep is structured and how it evolves as your child grows up, it will hopefully give you some important clues to understand why they sometimes wake at night, have difficulties falling back asleep or wake up early in the morning.

If you feel that your childʼs sleep patterns are derailed in a way that it affects your and / or your childʼs wellbeing, it is time to act.

Often, already small adjustments can make a big impact.