When children are awake for a longer time than their bodies can tolerate, their brains detect that an “extra boost” is needed to stay alert and so release cortisol (also known as the “alert” hormone) into their systems to help them stay up.
For adults, we know this as catching our second wind, when you push through those initial feelings of tiredness and, after spending a prolonged period awake, temporarily cease to feel drowsy, despite objectively needing sleep.
For children, it’s a little more problematic. Because your child’s system is now awash with accumulated cortisol that has nowhere to go, he/she now struggles to fall asleep and stay asleep. This can cause a whole host of sleep issues including:
Lots of crying, struggling, when trying for sleep
Frequent night wakings
Early morning wake ups
Short and disrupted naps
How do I avoid these issues?
Prevention is the best cure with overtiredness, so you’ll be wanting to put your child down for sleep before he/she overtires to prevent that cortisol build up.
As for knowing where your child’s threshold is, this takes a bit of practice, but generally it’s a simple 2-stage process.
Step 1: You figure out the right awake window for your child based on their age, and watch the clock so (a) you don’t wait too long to put your child down for sleep, (b) you don’t overstimulate your child towards the end of their awake window. As a general rule of thumb:
0-3m olds should be awake for <45mins
3-6m olds can be awake for 1-2 hours
6-9m olds can be awake for 2-3 hours
9-12m olds can be awake for 3-4 hours
12-24m olds can be awake for 4-6 hours
These ranges, however, are only the starting point as each and every child is different and unique.
Step 2: The next step involves you getting familiar with your child’s tired signs. As you draw closer and closer to the end of the age-appropriate awake window, look out for some of the common signs of tiredness. (See in this link The Baby Sleep Deprivation Symptoms)
A common mistake for the older age groups
In my experience, for parents with older children (commonly, children 11m and up), the tendency is to allow their children to sleep when they “seem tired”.
The issue with that is this: the tendency with this age group is that they’re more concerned with the fun they will miss out on when they’re asleep. This means they often fight any sleepy feelings/signs, and with their energy levels, they can often push their thresholds quite far. By the time they actually start showing signs of flagging, they’d be way past their awake window.
A good gauge for you on whether your child is overtired is to look at how much sleep he/she’s getting in a 24h window. An 11 month to 3-year-old should get at least 12-14h of sleep total. If your child is getting much less than this, then chances are he/she won’t be functioning at their best levels. You will likely see this manifest in behavioural issues such as:
Inability to play independently
Lack of appetite
Inability to emotionally regulate
If your child is experiencing these, then the best thing you can do to remedy the situation is to carry out the 2 steps above, to remedy the chronic overtiredness.