It is very normal for toddlers and young children to wake during the night. Some of those wakings are important and necessary, like for comfort, connection, or feeding. But sometimes children wake even when they don’t really need anything. If you are hoping to reduce those extra wakings, one of the most impactful areas to look at is something simple: light.
We’ve known for a long time that light is one of the strongest cues for our circadian rhythm, which is the body’s internal clock that tells us when it’s time to be awake and when it’s time to rest. Bright light during the day helps anchor that rhythm and supports nighttime sleep. Softer, dimmer light in the evening helps melatonin rise so the body can settle into sleep.
Recently, a study was published that reinforces what we already know about the importance of light for sleep. The researchers didn’t study real children directly, but instead built a mathematical model using decades of research on how light, circadian rhythms, and sleep pressure work in kids. They ran different “light schedules” through this model to see what would happen to sleep, and the results are really interesting.
Key Findings From the Study
Brighter days mean fewer night wakings
- The model showed a clear relationship between the brightness of daytime light and the number of nighttime wakings.
- When daytime light was below 300 lux (that’s about the brightness of a typical indoor living room), the model predicted more frequent wakings.
- At very dim levels, closer to 100 lux (like a softly lit hallway), wakings happened every single night.
- When daytime light reached about 1,000 lux (similar to being outdoors on a cloudy day or sitting by a bright window), the model predicted much more consolidated sleep.
Evening light delays melatonin
- Bright light in the evening suppressed melatonin, which made it harder to fall asleep and more likely that kids would wake in the night.
- The model suggested that children may be especially sensitive to evening light exposure, making it a really important time of day to dim lights and keep the environment calm.
Weekend delays in both morning and evening matter
- When the model simulated later morning “lights-on” times on weekends, there was no big impact if the delay was under about 1.5 hours.
- When mornings were delayed more than 1.5 hours, weekend nights became more fragmented and sleep timing shifted later. It took a few days for the sleep rhythm to realign.
- Later “lights-off” times in the evening had a similar effect, and the model showed that kids were even more sensitive to evening delays. More evening light meant more fragmented sleep and later circadian timing.
What This Means- How to Apply it at Home
You do not need to chase perfection, but if you are struggling with your child’s sleep, specifically night waking, light and consistency is one area you may want to prioritize. Think of light as one supportive piece of the sleep puzzle. If your child is waking often at night and you’d like to experiment, here are some ideas that may help:
- Start the day with light. Open the blinds when your child wakes up, or step outside for a few minutes. Morning light is a powerful way to set the circadian rhythm.
- Brighten their daytime environment. Spend time outdoors if possible, or play near windows. If your home is darker, consider adding brighter lamps during the day.
- Soften light in the evening. About an hour before bedtime, start dimming overhead lights. Use warm-toned lamps instead. If you need a nightlight, red-based lights are the least disruptive to melatonin. I like these red night lights, and this touch lamp set to the red light setting for nighttime nursing and changing diapers.
- Think about blue light. Try to avoid screens close to bedtime. If screens are unavoidable, blue-light–blocking glasses may be an option for older toddlers.
- Aim for consistency, but with flexibility. Try to keep wake and sleep times fairly steady, including on weekends. Shifting by less than an hour is usually fine. Once delays get beyond about 1.5 hours, especially in the morning, sleep disruption is more likely. At the same time, you don’t need to be rigid. If your family has a late morning or evening now and then, that’s okay. The idea is not perfection, but being aware that bigger shifts can impact sleep.
- A note on early rising: This is a challenge many parents run into from time to time, and based on the research, my recommendation is to try not to expose your early riser to bright lights too early. Rather maintain a dim room (you may have to stay in the room and snuggle with your child) until their desired wake up time so that early exposure to light does not impact their circadian rhythm.
This study confirms what has been known for a long time: light is a powerful influence on sleep. The brightness of daytime light is directly linked to the number of night wakings, and dim evenings help the body prepare for rest. Morning and evening timing matter too, especially when weekend routines are very different from weekdays.
At the same time, remember that light is only one piece of the sleep puzzle. Many factors influence your child’s sleep, from temperament and development to environment, routines, underlying health and medical issues, and daytime activity. If your toddler is waking at night, it could be normal. Check out my red flags blog post if you feel like it isn’t normal. But if you are looking for ways to reduce unnecessary wakings, optimizing light is one supportive step to consider.
And if you want to dive deeper into all of the many factors that impact toddler sleep, check out my comprehensive toddler sleep e-course, where I walk you through the big picture and how to support your child’s sleep holistically. Alternatively, if you feel you need more 1:1 support, schedule a call with Jenn for holistic and responsive sleep support that feels good.
Reference
Yao, Y., & Booth, V. (2025). External light schedules can induce nighttime sleep disruptions in a Homeostat-Circadian-Light model for sleep in young children (arXiv:2507.19772). arXiv.
