How Blue Light Affects Sleep: Understanding the Science Behind the Advice
You’ve probably heard the common advice: “no screen time before bed” or “blue light is bad for sleep.” But what does that really mean, and why should you care? Does blue light actually affect your sleep?
It’s easy to brush off advice if we don’t fully understand it—kind of like when our parents told us not to swim for 30 minutes after eating, but didn’t explain why. Without knowing the reasoning, we were more likely to ignore it.
But some advice, like “eat your veggies to stay healthy,” sticks with us because we eventually understand its value. Now, as adults, we know the importance of nutrition. My goal here is to give you that same “aha” moment about blue light so you’ll understand why avoiding screen use before bed really can improve the quality of your sleep.
How the Human Eye React to Light
Let’s start with a quick look at how light affects our eyes. You might know about rods and cones—the cells that help us see in dim light and recognize color. But there’s another type of cell called intrinsically photosensitive retinal ganglion cells (don’t worry, you won’t need to say that five times fast!). These cells are highly sensitive to blue wavelengths—naturally produced by the sun and artificially produced by cell phones, tablet screens, computer monitors, and TVs.
When blue light hits these cells, it sends signals to the brain’s suprachiasmatic nucleus (SCN). The SCN is our body’s biological clock, managing our sleep-wake cycle.
Why Blue Light Disrupts Sleep: The Melatonin Connection
Here’s where it gets tricky: your body naturally produces melatonin, our sleep hormone, when it starts to get dark. But blue light confuses your brain, making it think it’s still daytime, which delays the release of melatonin and makes it harder to fall asleep.
To make matters worse, our eyes have a sensitive period when they become even more affected by blue-light exposure- late at night and early in the morning. So if you’re scrolling social media, staring at your phone screen, or catching up on work, using your computer screens, the amount of blue light, blasted at your eyes, tricks your brain into staying alert. Even small lights—from light-emitting devices like your electronic charger—can disrupt your sleep patterns, especially when you wake up briefly from a sleep cycle in the middle of the night.
Light our eyes used to be exposed to in the evenings
The Modern Impact of Artificial Light on Sleep
It’s worth noting that this whole blue light issue is relatively new. Before modern lighting, our bodies’ circadian rhythms were in sync with the natural light-dark cycle. People relied on sunlight during the day and the warm glow of fires, candles, or lamps at night. These light sources had longer wavelengths, which didn’t interfere our production of melatonin.
But with today’s artificial lighting, especially from electronic devices, light-emitting diodes (LED), and florescent lights, we are constantly exposed to short-wavelength light. While it’s great for energy efficiency and productivity, it’s not doing our sleep any favors, and in fact could contribute to sleep disorders. The bright light from our digital devices mimics a sunny day, which throws off our body’s circadian clock and leads to sleep disturbances.
The light our eyes encounter nowadays
How Natural Light Cues Our Sleep-Wake Cycle
Throughout the day, the light waves we experience naturally change. The peak of blue light exposure happens around midday (Fun Fact, that’s why the sky appears blue). As the day progresses and the sun begins to set, the light has to travel through more of the Earth’s atmosphere. This filters out much of the shorter wavelengths from blue light, leaving behind the longer wavelengths. Hence these different wavelengths result in different light colors, such as the pink, orange, and red colors of light we see at sunset.
When we see these warmer colors (like red light and orange light), our brain recognizes that it’s almost sleep time and our melatonin levels will rise. But nowadays, the average person misses out on those natural cues. Instead, we’re glued to our electronic screens, soaking in artificial light levels that tell our brain, “Hey, look, it’s daylight hours still!” No wonder our internal clocks are confused.
Negative Effects of Poor Sleep
Ignoring the effects of blue light on poor sleep doesn’t just make you feel groggy the next day—it can lead to serious health issues. Sleep deprivation has been linked to weight gain, as it throws off the balance of hunger hormones like ghrelin and leptin, making you more likely to crave unhealthy foods.
Lack of sleep is also a major risk factor for diabetes. Poor sleep affects your body’s ability to process glucose, which can lead to higher blood sugar levels and an increased risk of type 2 diabetes.
Sleep has a significant impact on heart health as well. When you don’t get enough sleep, it can raise blood pressure and cause inflammation, both of which increase the risk of heart disease.
And let’s not forget how important sleep is for cognitive function. Memory, concentration, reaction times, and decision-making all suffer when we don’t get enough rest. Our mental health and cognitive performance rely on the positive effects sleep offers our brain.
So, when we let the influence of blue light mess with our sleep, we’re not just sacrificing a good night’s rest—we’re also putting our long-term health at risk.
Simple Tips to Reduce Blue Light Exposure
Don’t worry, you don’t need to banish screens entirely to get better sleep. Here are a few easy ways to reduce blue light exposure and help your body prepare for rest:
- Limit Screen Time Before Bed: Aim to stop using your electronic devices at least an hour before bedtime. This gives your body time to start producing melatonin naturally.
- Turn on Night Mode: Most devices have a dark mode that reduces blue light. It’s a good idea to switch it on in the evening to minimize blue light exposure. Alternatively, there is also an way to switch devices to a greyscale mode. (You can learn more about that here from a digital boundaries coach)
- Try Blue-Light-Blocking Glasses: If you need to use screens at night, blue light-blocking glasses can help. Make sure they have an amber tint—those are more effective for promoting the production of melatonin. Clear light glasses, that say they help with blue light, are used for digital eye strain but do not have a strong enough blue light filter to help with preparing for bed.
- Adjust Your Lighting: In the evenings, use dim, warm-colored light sources at home. A great way is to opt for table lamps over bright ceiling lights to create a more sunset-esque environment.
- Wind Down with Calming Activities: Replace screen time with relaxing activities like reading a book, meditating, or doing some gentle stretching. This tells your body it’s time to wind down. (You can read my wind down blog for more tips on this!)
Blue Light Really Does Affect Our Sleep!
So let’s do something about it!
In our screen-filled world, being mindful of blue light exposure is key to improving sleep. By understanding how our bodies respond to light and making small adjustments to our nighttime routines, we can improve sleep quality, protect our health, and wake up feeling refreshed. Let’s make restful sleep a priority—because we all deserve to wake up feeling our best. 💜 🧸
FAQ About Blue Light and Our Eyes:
My household light has a setting for either warm light or daylight, which should I use to protect my sleep quality?
A lot of time during the day, you can use whichever setting you prefer. In the evening, though, I suggest switching to yellow light. That softer glow has longer wavelengths, which more closely mimic the natural tones of sunset. White light, on the other hand, gives off shorter wavelengths—blue or bright white—that send the wrong signal to your eyes, tricking your brain into thinking it’s earlier in the day than it really is. If possible, also enable a dimming feature so the light gradually softens as the evening goes on.
If the American Academy of Ophthalmology doesn’t recommend blue light blocking glasses, why do you?
The AAO reassures us that blue light from devices doesn’t damage our eyesight—and that’s good news! However, as a sleep specialist, my concern isn’t eye health, but rather how blue light impacts our sleep. I recommend using blue light blocking glasses to reduce the amount of blue light reaching your eyes and sending wake-up signals to your brain.
I heard blue light therapy devices are helpful for seasonal affective disorder and shift workers. Are you saying you don’t like blue light therapy because blue light is bad?
I’m not saying blue light is bad for us. I’m simply explaining how it affects the brain and when it’s best to avoid it. People who have SAD can definitely benefit from blue light therapy devices, however, they should still aim to use them in the morning hours. If they use them in the evening then they risk wreaking havoc on their sleep, which would actually exacerbate their disorder.
For shift workers, the goal is different. Since they’re trying to reset their internal clocks to work the night shift and to stay awake when the sun isn’t out, blue light therapy devices can actually be really useful. In this case, they’re intentionally using blue light to help the brain stay alert.