“Wake windows” are a newly popular concept in infant and toddler sleep. In a nutshell, “wake windows” are intervals between naps. They are also known as “awake windows” or “baby wake windows”. Although they have some basis in sleep science, there is little evidence that systems based around wake windows improve baby and toddler naps. They also seem overly complicated to me. But some parents swear by them. So let’s delve a little bit deeper.
What are wake windows?
“Wake windows” are defined as the length of time (“windows”) during which babies and toddlers should be awake. This term also seems to refer to systems which promise to simplify the process of getting babies and toddlers to nap.
This is not a concept that is taught, discussed, or researched in medical school or in the world of pediatric sleep medicine. A Pubmed search pulled up zero references on the term. When I reviewed Google Trends, this is a relatively recent topic of interest, popping up in searches only in the last few years
To me, this feels like sleep regressions, another topic which has seemed to gain traction in the world of sleep consulting and parent message boards, not academic research. I don’t think that this empirically disqualifies them, because many effective medical treatments and technologies start getting used before we understand WHY they work.
How do you use wake windows?
Personally, I don’t use wake windows in my practice. But here is a typical example of how you are supposed to use them to get to better naps.
In a nutshell, you look at the age of your child, then put her down for a nap after she has been awake for a set period of time (the wake window). (I took this from here).
- Age-by-Age Wake Windows
- Newborn wake window: 60 to 90 minutes
- 4 to 6 month old wake window: 1.5 to 2.5 hours
- 7 to 9 month old wake window: 2 to 3.5 hours
- 10 to 12 month old wake window: 2.5 to 4 hours
- 13 to 15 month old wake window: 2.5 to 4.5 hours
- 16 to 18 month old wake window: 4.5 to 5.5 hours
- 18 month old+ wake window: 5 to 6 hours
OK. This seems straightforward, although I have no idea where these numbers came from (see below). Different websites have different numbers. But there are ranges, so that’s OK. So what do you do with them?
Here’s were it get’s complicated. You are supposed to adjust these windows based on the time of day, how many naps have occurred, and the duration of naps. It’s. . .complicated. (See below).
What is the scientific basis behind wake windows?
To understand wake windows, you need to understand sleep drive. Simply stated, sleep drive is one of the main factor that determines when someone falls asleep. Sleep drive increases very quickly in early childhood. As children get older, it accumulates more slowly, meaning that children can go longer and longer without sleeping. That’s why, for example, babies nap frequently, two and three year olds nap once a day, and kindergarteners generally don’t nap. (I have an article on sleep drive here if you want to learn more.)
During early childhood, the speed at which of sleep drive increases changes quickly. In the first four years of life, children go through stages where they sleep for
Four naps a day –>Three naps a day–>Two naps a day–>One nap a day–>No naps a day
The problem is, I can’t tell you when those transitions will occur. Predicting when this happens is painful, though, ESPECIALLY in infancy as babies go go from napping four to five times per day at birth, to likely napping twice a day by one year of age. Due to the neurological immaturity of infants, their napping schedules can vary day to day, especially early in the first year of life. Your baby may, say, take three naps on one day, two naps the next, then three naps again.
This is the reason parents struggle with napping. It feels like you are reinventing the wheel every few days, resulting in missed naps and nap strikes. Each missed nap results in irritable kids and stressed parents. For parents who are often overwhelmed, this feels like torture.
That’s why the idea of wake windows has gained traction. These systems promise a cookbook approach to napping timing which promises to streamline the process.
What’s the problem with wake windows?
First off, if you’ve used wake windows and your baby is sleeping well, that’s great. Often, any plan beats no plan. But if you are considering trying this out, recognize that these are complex systems with little basis in science.
Here are my two primary issues with wake windows as a system for addressing nap problems.
1. The numbers don’t seem to have any scientific basis.
Here’s information on daytime sleep duration in infancy and early childhood, from a seminal paper on the topic (Iglowstein, I., Jenni, O.G., Molinari, L., Largo, R.H., 2003. Sleep Duration From Infancy to Adolescence: Reference Values and Generational Trends. PEDIATRICS 111, 302–307. https://doi.org/10.1542/peds.111.2.302) Although there are some limitations in this paper (they studied 493 Swiss babies– as you can imagine, not the most diverse population you can find), this is a good reference for looking at sleep duration.
First off, there is a huge amount of variability in how much individual children nap during the day. This graph shows the amount of time children in the the study sleep during the day over time. Each of the lines going from left to right represents the typical amount of time children were sleeping during the day at different ages. The spread (from the 2nd to the 98 percentile) is very wide in early infancy and gets narrower over time. This means that the amount of time that children sleep during the day is highly variable in the first year. For example, look at the arrows at six months of age showing the average daytime sleep duration at the 25th and 75th percentiles. (note that this means that 25% of children and 75% of children sleep less than these values during the day.) Six month olds at the 25th percentile sleep about 2.5 hours per day; those at the 75th percentile sleep about 4.5 hours during the day. Half of children fall between those two numbers. Thus, the amount of time babies sleep during the day is really difficult to predict.
Next, look at the data from six to eighteen months. Some kids are napping two or more times per day, but some aren’t. All we know is the proportion reduces over time.
The take home: Napping is highly variable from child to child. We do know that sleep requirements tend to be stable in individual children. This means that children who need less sleep in infancy continue to need less sleep as they get older. (And the children who need less sleep are often the ones whose parents are struggling with daytime and night time sleep patterns). But the numbers describing how long wake windows should be at various ages do not seem to be based on any scientific evidence.
2. The systems are hard to follow
I don’t mean to pick on the obviously kind and well intentioned author of the post above. Maybe I’m an idiot. (In fact, it’s quite likely I’m an idiot).
But I’m an expert. And I would struggle to explain and implement a system like this with tired parents.
As far as I can understand:
- Wake windows should increase during the day. So a four month old will go down at 1.5 hours for the first nap but 2-2.5 hours for the next nap.
- Nap duration is a factor– if the nap are long or short you may need to adjust wake windows.
- A skipped nap should drastically shorten wake windows.
Here’s a description from a website I read when I was researching this article (I’m not linking as it appears to have been taken down):
” When referencing these ranges, keep in mind that the shortest wake window is always going to be before the first nap and the longest wake window will be before bed. So for example, a 4-month-old should be going down for their first nap around 1.5 hours from when they woke up that morning and should go down for the night about 2 to 2.5 hours after they wake up from their last nap.
There are times when you will need to adjust wake windows based on how long your child naps. My rule of thumb is that if baby naps 40 to 45 minutes or less, shorten the next wake window by about 45 minutes (or in some cases up to an hour) to prevent baby from becoming overtired. If your little one were to only sleep 20 minutes, for example, following a full wake window (based on their age) would most certainly result in a cranky, overtired baby, which causes a cycle of short naps. To avoid this, whenever naps are short, we shorten the next wake window.”
I feel bad singling out this post. Clearly the author is well intentioned and wants to help tired parents. But this made my head spin.
My child isn’t napping! What should I do?
As well as the Times article, I have more information here about how to proceed if you are struggling with naps:
In my New York Times piece, I put in the following recommendations
- Make sure your expectations fit in the expected frequency and duration of naps for age.
- If night time sleep is bad, work on that first
- Replicate your child’s bedtime routine in miniature before nap time
- Don’t panic during nap strikes
- Recognize when your child is ready to give up a nap.
The best thing to do is to look for signs of sleepiness (yawning, rubbing eyes, dozing off). If you’re not sure, maybe the list of wake window intervals is useful to you, feel free to try it out. But don’t worry if it doesn’t work for your child. And don’t feel like you need to try wake windows.
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The idea of playing with your child’s sleep intervals to fine what works is a good one, and, generally, these intervals will get longer with time. Tracking your child’s sleep can be really helpful as well so you can recall any insights you have.