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Understanding babies’ sleep cycles.

Baby sleep cycles are quite different from yours, starting from the amount of time each of you spend sleeping. As you are probably already aware, your baby needs much more sleep than you do!

Here is a simple guide for how much sleep a baby needs in a 24 hour period, depending on their age:

  • Newborns need around 16 hours
  • 3 month olds need around 15 hours
  • 12 month olds + need around 12 hours

As we know, all babies are different, so not every baby will need exactly this amount, but loosely this is what you should be working towards. Of course, your baby will not take all this sleep in one long stretch, but in sleep-wake cycles throughout the day. You only need to consider the size of a baby’s stomach (hint: tiny!) to know that they will need to wake more often to fill it up. Babies need to eat quite frequently just to keep functioning.

To properly compare the sleep cycles of adults and babies, let’s start by taking a look at your own sleep cycles*. When adults fall asleep, they go through several sleep stages, such as deep sleep and REM (or active) sleep. The latter stage is actually essential for the healthy life of any adult and is known widely because of its association with dreaming. What’s more, even though the skeletal system is temporarily paralysed, brain activity during this stage resembles that of the waking brain – the eyes move quickly beneath the eyelids and breathing often becomes irregular. From beginning to end, an adult’s sleep cycle lasts about 90-100 minutes. At the end of a sleep cycle, an adult either wakes up or begins a new cycle by returning to an earlier stage.

What does a baby’s sleep cycle consist of?

A newborn’s sleep cycle is much simpler with only two stages – active and non-active sleep. Your baby’s sleep cycle is also much shorter, with an average of 45-60 minutes for the first nine months, often even shorter. It looks la bit like this:

  • When a baby first falls asleep they go into active sleep, which is very similar to REM sleep for adults. During this stage, babies are also more likely to wake up. A newborn will spend about 50% of his or her sleeping cycles in this stage, as opposed to an adult, with only 20%.
  • About halfway through a sleep cycle, the baby falls into non-active sleep, which is characterised by slower, rhythmic breathing, less movement and no eyelid fluttering. Non-active sleep is the end of the sleep cycle, which means that the baby will either wake up or return to active sleep.

From six months onwards, babies develop more stages that resemble adults and gradually replace non-active sleep. The duration of their sleep cycles also lengthen and the time spent in active sleep shortens.

So, babies are not born with the sleep-wake cycles your body works with. They are much lighter sleepers than adults, because they spend so much time in active sleep. This is why it can take anywhere from six months to one year of age for a baby to sleep through the night like you do. From about six months, they can sleep for longer stretches, but it can take a while for them to build to a solid, uninterrupted 8-12 hours sleep with no wakefulness whatsoever.

Despite all these challenges about the way babies are wired for sleep, sleep remains crucial in the early months and years for brain development, especially forming the vital connections between the brain hemispheres which are important to language, relationships and reasoning. 

* https://www.verywell.com/the-four-stages-of-sleep-2795920