The science behind "wake windows" and why they don't matter as much as you think
Are you constantly trying to tweak your child’s "wake windows" to improve sleep? Have you heard that your child needs a specific amount of awake time and that if you stretch it too far, your little one will become overtired and won’t sleep—but if you cut it short, your child will be undertired and won’t sleep either? If so, you’re not alone!
It seems the latest social media trend in baby and toddler sleep is to promote the idea that magical "wake windows" are the secret to ensuring your child gets enough sleep at the right times. While it’s important to avoid extremely short or overly long wake times for your child’s age, the concept of "wake windows," as often described by influencers, is oversimplified and misleading. In fact, rigidly following wake windows can lead to problems like split nights or early waking. Obsessing over wake windows can also result in parents developing orthosomnia.
In this blog, we’ll break down the science the sleep drives and explain why wake windows alone don’t work. We’ll also give you practical strategies to help your baby get enough sleep at the right time.
The Science
To understand why wake windows aren’t the magic solution, it helps to know about the two main drivers of sleep:
Homeostatic Sleep Pressure (Sleep Pressure): Sleep pressure is simply the build-up of sleep need over time. Sleep pressure comes in two forms, acute and chronic. Acute sleep pressure is simply how long your child has been awake. The other, often ignored type of sleep pressure is chronic sleep pressure, which is the build-up of sleep debt over several days.
Circadian Rhythm: This is the body’s internal clock, which regulates sleep and wake cycles based on light exposure and timing.
These sleep drives interact in complex ways. The concept of wake windows focuses almost entirely on acute sleep pressure while ignoring chronic sleep pressure and circadian rhythm—two equally important factors.
How Does Acute Sleep Pressure Influence Wake Windows?
The longer your child is awake, the sleepier they’ll feel due to a build-up of a neuromodulator called adenosine in the brain. (Fun fact: caffeine blocks adenosine, which is why it helps adults feel alert!)
Younger babies can’t handle much sleep pressure and need to nap frequently, while toddlers can tolerate longer wake times—usually 4-6 hours. If acute sleep pressure was the only sleep driver, sticking to wake windows might work. But this ignores chronic sleep pressure and the circadian rhythm, both of which play critical roles in your child’s sleep timing and ability to sleep.
How Does Chronic Sleep Pressure Affect Sleep?
Chronic sleep pressure reflects your child’s accumulated sleep debt. For example, if your baby typically needs ~13.5 hours of sleep in 24 hours but only gets ~12.5 hours for a few days, your little one will build up sleep debt.
The good news is that your child's body will try to maintain homeostasis, which means your child may have a random long night or long naps to recover from experiencing a little chronic sleep debt. In most cases, you don't have to do anything to make your child sleep longer, your little one's body will self-regulate.
Many parents think the random long nights or naps represent their child's sleep needs. In many cases, this sets parental expectations for sleep too high. To get a better estimate of your child's sleep needs, calculate your child's average sleep amount over the course of a week.
Remember, sleep patterns naturally fluctuate. You don’t need to stress over small daily variations; only make adjustments if your child develops a severe sleep debt. If your child does seem to have a severe sleep debt, a strategic early bedtime may help relieve sleep pressure.
How Does the Circadian Rhythm Influence Sleep?
Your child’s circadian rhythm promotes sleep and wakefulness at specific times. Light is a signal to be awake. If your child's wake time is somewhat regular, your child's morning light exposure will be regular. This means the times when your child's circadian rhythm signals for sleep and wake will happen at about the same clock times each day.
It's important to know that the wake maintenance zone (AKA forbidden zone for sleep) is a time at the end of the day when your child's circadian rhythm strongly promotes waking. This can make it hard for a child to fall asleep earlier than their biological bedtime, except in cases of extreme sleep loss.
Why Wake Windows Alone Don’t Work
When your child wakes for the day, acute sleep pressure builds until your child has the first nap. But chronic sleep pressure and the circadian rhythm add complexity:
A child with sleep debt may be ready for naps a little earlier than normal or may have a random long night of sleep.
Your child's circadian rhythm will promote sleep around the same clock time each evening. This means that if you just stick to wake windows and ignore the circadian rhythm, you may end up with a sleepy, upset child who can't sleep!
what is the best way to determine when a child is ready for sleep?
Although sleep science can feel overwhelming, you don’t need to overthink it. Use these simple tips to guide your decisions:
Use Wake Windows for Daytime Naps—With Flexibility: Start with average wake times for your child’s age (see our Age-by-Stage Sleep Chart). Adjust based on your child’s cues and keep a sleep log for 1-2 weeks to find what amount of time between naps works best on average.
Use these times to estimate when your child will be ready for sleep. If your child seems very tired earlier than usual, it’s okay to put them down a little sooner. Conversely, if they’re alert and happy, you can stretch their wake time a bit.
Don’t Use Wake Windows for Bedtime: Unless your baby is under 3 months old, bedtime should remain consistent (e.g., within 30 minutes) to help stabilize the circadian rhythm.
Wake Your Child in the Morning: You don't need to be rigid about waking your child at an exact time each day, but starting your child's day at around the same time will help synchronize your child's circadian rhythm. It will also mean your child's first nap will likely happen around the same time each day. If your child wakes earlier than you would prefer, you can shift your child's circadian rhythm to achieve a later wake time.
Time the Last Nap Strategically: Adjust the last nap to end at an appropriate time before bedtime. For example, if bedtime is 8:00 pm and your child usually stays awake for three hours, aim to give your child a nap that ends by about 5:00 pm. This might require waking your child from an earlier nap or stretching your child's awake time between earlier naps to get the timing right.
Prevent Chronic Sleep Debt: Maintaining a consistent schedule with small day-to-day adjustments should enable your child to get enough sleep on a regular basis.
Final Thoughts
While social media makes wake windows sound like the ultimate solution, sleep science shows us that factoring in all of the sleep drives in decision-making is key. By considering both sleep pressure and the circadian rhythm, you can create a sleep schedule that supports your child’s overall rest and development.
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References
Wong, S.D., Wright Jr, K.P., Spencer, R.L., Vetter, C., Hicks, L.M., Jenni, O.G. and LeBourgeois, M.K., 2022. Development of the circadian system in early life: maternal and environmental factors. Journal of physiological anthropology, 41(1), p.22.
Kurth, S., Lassonde, J.M., Pierpoint, L.A., Rusterholz, T., Jenni, O.G., McClain, I.J., Achermann, P. and LeBourgeois, M.K., 2016. Development of nap neurophysiology: preliminary insights into sleep regulation in early childhood. Journal of sleep research, 25(6), pp.646-654.
LeBourgeois, M.K., Wright Jr, K.P., LeBourgeois, H.B. and Jenni, O.G., 2013. Dissonance between parent‐selected bedtimes and young children's circadian physiology influences nighttime settling difficulties. Mind, Brain, and Education, 7(4), pp.234-242.
Bathory, E. and Tomopoulos, S., 2017. Sleep regulation, physiology and development, sleep duration and patterns, and sleep hygiene in infants, toddlers, and preschool-age children. Current problems in pediatric and adolescent health care, 47(2), pp.29-42.
Chan and Au, 2024. Circadian Development and Homeostatic Sleep Pressure. HOT TOPIC-Assessment and Treatment of Infant Sleep: Medical and Behavioral Sleep Disorders from Birth to 24 Months, p.25.