There are few more confusing phrases than “sleep breeds sleep”, after all it’s so counter intuitive.
Logically you would think that a long sleep would leave your baby refreshed and alert, not sleepy, and that a tired baby would be more likely to sleep well.
Yet, people keep saying that the answer to a baby who doesn’t sleep well is an early bedtime, or an extra nap.
It doesn’t seem to make sense, but the answer lies in sleep hormones.
Our bodies are complex things and there are many influences on them, but there are two main hormones that it’s worth considering when it comes to sleep.
I’m not a biologist, and you don’t have to be one either so this is a very brief summary that will give you a practical understanding rather than an in-depth review.
First, levels of the “sleep hormone” melatonin go up when you are asleep.
Adults usually have very low levels of melatonin during the day, but they naturally rise in the evening in preparation for a good night’s sleep.
In a baby or young child there is less time between naps for the levels to drop and they tend to stay a little higher.
But if your baby misses a nap their melatonin level might drop more than usual, making it harder for them to fall asleep and stay that way.
Melatonin is so effective in helping your child to sleep that it is sometimes prescribed to people with sleep problems, so it’s great to encourage its natural production.
The things that indicate evening in a natural environment, darkness and a cooler temperature, trigger melatonin ready for bedtime.
So it’s best to avoid bright lights in the hour before bed and keep your baby’s sleep space at around 18 degrees.
Cortisol has a bad name as “the stress hormone” and it’s true that it is produced when you experience stress.
However, in some ways it could be more accurately described as the hormone of alertness and levels naturally fluctuate throughout the day, even a completely stress free day.
Cortisol levels should be low at bedtime, when you don’t want your baby to be alert, then rise gradually overnight until they get high enough to wake them (unless of course they wake sooner for a feed).
If the cortisol level is too high at bedtime it will reach the level that wakes your baby up much sooner than it otherwise would, which can mean an early waking or waking in the night and struggling to get back to sleep.
Of course a baby won’t be worrying about things in the way an adult might but they could be stressed by overstimulation or by overtiredness.
Making sure they get enough rest and have a calming bedtime routine can help to keep cortisol levels lower.
So, there it is in a nutshell.
Sleep begets sleep because the hormone changes during sleep make it easier to fall asleep, and stay that way.
Which is why I sometimes suggest an earlier bedtime, or longer nap, for a little one who struggles at night.