How Light Wavelength Affects Your Baby's Sleep
We can’t remember where we saw it, but we distinctly recall Matthew McConaughey talking about the simplicity of raising a baby, saying, “They eat, they crap, they sleep, and if they’re crying they need to do one of the three and they’re having trouble doing it. Real simple”
While we agree with him to an extent on the first part, we vehemently disagree with the second one. Any one of those three elements can be caused by so many factors, either on their own or in combination with others. Identifying the problem may be simple, but trying to determine the cause is a much trickier ordeal.
When it comes to sleep, there are so many factors that might be impeding your little one’s ability to just lay their head down and go to sleep when they’re tired. Hormone levels may be out of balance, they may be in some kind of physical discomfort, too hot or too cold, they may be overtired or not tired enough... the possibilities can seem endless.
However, as child sleep experts, we can tell you that one of the most prominent causes of fractured sleep in our little ones is light. Exposure to blue light has been shown to decrease baby’s feelings of drowsiness, increase the time it takes for them to fall asleep, decrease deep sleep, and affect their ability to stay asleep.
Light, obviously, is everywhere, and has been since day one. Our ancestors were better suited to hunting and gathering during daylight hours while the light was bright enough for our eyes to pick up movement and colors. But we needed rest as well, so better to sleep in the night when we wouldn’t be as efficient and at a disadvantage to predators whose eyesight was more acute in the darkness.
Over time, our bodies began secreting hormones to help us sleep when it began to get dark (melatonin) and to provide stimulation when it got light (cortisol).
This all worked pretty beautifully right up until a technological breakthrough that, quite literally, changed everything. In 1879, the world was introduced to the electric lightbulb, and before long, we had access to light at all hours and in every room of the house.
“Wait,” you may be thinking, “What about candles? People didn’t live in the dark until lightbulbs were invented!”
And you’re absolutely right, but the big difference between fire light and the light from electric lightbulbs is the wavelength.
We don’t want to get too nerdy on you here, (you can get the science-y stuff straight from NASA if you’re interested) but visible light comes in different wavelengths. Longer wavelengths appear red or yellow and shorter wavelengths appear white or blue.
So, as the lightbulb became more accessible, and as the filaments evolved, we started swapping out the long wavelength red or yellow light from candles for the short wavelength blue light from electric bulbs.
Why does that matter? Well, to take it back to our ancestors again, the light we get from the sun during the day comes directly down through the atmosphere, and that means it’s not being refracted, which results in short-wavelength or “blue” light. So when your little one asks you why the sky is blue, that’s actually a big part of the answer.
When the sun starts to set, it refracts off the atmosphere which stretches out the wavelength, creating red light. Again, a big part of the reason the sky turns red during a sunset.
So our bodies and brains evolved to recognize these cues from the sun, and started secreting those hormones at the appropriate time of day to either help us wake up and get going, or to settle down and go to sleep.
But once we brought blue light into the house, you can see how our brains started to get confused. Our eyes started picking up “daytime” light well into the night, our brains kept secreting cortisol to keep us alert, started blocking the release of melatonin, and sleep suddenly found itself fighting an uphill battle.
Fast forward about a hundred years and we see the invention of the television, which emits a ton of blue light. Not long afterward, computer monitors, LEDs, smartphones, and tablets are a favorite pastime for our little ones, which can have a huge impact on their sleep.
So, if blue light impedes your baby’s sleep, will red light actually improve it?
To a large degree, the jury is still out on this debate. Some studies suggest that short-wavelength red light can indeed help stimulate melatonin production, but others have shown that exposure to red light, while much less inhibitive to sleep than blue light, resulted in similar or slightly less melatonin production than if baby just slept in the dark.
In essence, a red light in the nursery isn’t likely to help improve your little one’s sleep, assuming they’re already sleeping in a dark room. However, if you need a light in the nursery for diaper changes or nighttime feedings, red light is absolutely, positively the way to go.
Some other light management tips that will help your baby sleep better at night include:
Turn the lights in the house down (or off, if possible) around two hours before baby’s bedtime
Turn off all tablets, phones, TVs, or any other electronic devices at least two hours before bed.
Don’t allow your little one to use electronic devices in their bed at any time of day.
Put a piece of tape over any lights emitted by devices in your baby’s nursery.
Use a red or yellow light during baby’s bedtime routine activities. (Bathtime, bedtime stories, etc.)
Let us just say in closing, we love technology! We love the convenience that our phones provide, we watch what we would consider to be a reasonable amount of TV, and we think that, properly managed, tablets provide a great source of free entertainment and educational opportunities for babies. We are not trying to suggest that you should throw every blue light-emitting device in the trash and go back to candlelight in the house. As long as you know the facts about how they can affect your baby’s sleep, it should prove relatively easy to make a few modifications and create a few rules around their usage so that they have almost zero impact on a long night of sweet, restorative sleep for your whole family.