HERE IS WHY!
One of the five components to consider with infant and toddler sleep is having your child sleeping at the right time(s) of day. Two processes occur within our bodies that contribute to this being the case. One of the processes is something you are probably already familiar - circadian rhythm or biological clock. However, another process that is not often discussed is sleep pressure.
When we are awake, a chemical called adenosine builds up in our brains. The more adenosine that builds up, the more tired we become. This is referred to as sleep pressure. In other words, the longer that we are awake, the more our urgency to sleep increases.
When we sleep, our brain disposes of the adenosine. Thus, decreasing our sleep pressure and, often times, allowing us to wake rejuvenated.
Sleep pressure is one of my favorite topics regarding sleep because it is one that often brings that "Aha!" moments to parents.
Let’s talk about this in relation to your child.
Here is a scenario that has happened to almost all parents and several care givers.
You are heading home from an outing. You are doing your best to get your child home for a nap in her bed. However, your child falls asleep within the last ten minutes of your drive. You are most likely anxious because you know that the chances of them taking a good nap is now shot.
But why is this the case?
You see. Your child falling asleep for even five minutes has now depleted some of that adenosine buildup and, although it still exists, their sleep pressure has now decreased. They had a short catnap to rejuvenate them and are no longer tired enough to fall sleep. But we know that they will be a hot mess within a short matter of time if a nap does not occur!
Now, as I mentioned, there are two processes that make sleeping at the right time of day important - the circadian rhythm and sleep pressure. These two factors do not affect one another. Meaning the following. One, the circadian rhythm continues with its usual ups and downs regardless of the amount of adenosine built up. Two, adenosine continues to build up when you are awake and to be depleted when you are sleeping regardless of where you are with your circadian rhythm.
So if a child is napping twice a day, when is it a good time to take those naps?
The answer is when the circadian rhythm is dipping AND when enough sleep pressure has built up to cause your child to have an urgency to sleep. These two go hand-in-hand when it comes to whether or not your child will have an easy time falling asleep for nap time or bedtime. For a two-nap schedule this generally happens around 9AM and somewhere between 12PM and 1PM. Both times when sleep pressure has built up and the circadian rhythm is naturally at a low.
The timing of sleep is very important. Do your best to preserve nap times so that they occur at the right times of day instead of short catnaps here and there while out on the go.
Why We Sleep: Unlocking the Power of Sleep and Dreams, by Matthew P. Walker, Scribner, an Imprint of Simon & Schuster, Inc., 2018, pp. 27–35.