Here's What Blue Light Before Bed Can Do to Your Circadian Rhythm — and How to Avoid It
As dedicated as I'm trying to be about my yearlong goal of getting better sleep, one habit I can't seem to kick is using tech before bed. I'm a big fan of binging YouTube videos, catching up on The Bachelor, and reading news stories from my comfy bed. Sometimes I'll be working late. Other times I'm FaceTiming my boyfriend. If there's an excuse out there to keep me scrolling instead of sleeping, I'll find it.
This is a common problem, and one that really can screw up your sleep. At first, I'm too distracted, entertained, and awake to want to power down. Then, when I finally do turn in for the night, my brain is still buzzing from the stimulation. I'm lying in bed feeling wired instead of sleepy.
What is it about our devices that makes it so hard to go to sleep? You may have heard of a little thing called blue light, which is a wavelength of visible light produced naturally by the sun and artificially by our devices. Natural blue light during the day can help you stay awake and even provide a mood boost. But when you're overexposed to it, especially from your devices and especially at night, it can wreak havoc on your sleep-wake cycle and your sleep quality in general.
Blue Light Disrupts Your Circadian Rhythm
Blue light is processed by special photoreceptors in your eyes, which in turn stimulate different parts of your brain, according to Mark Wu, MD, PhD, an associate professor of neurology at Johns Hopkins who specializes in sleep and circadian rhythm disorders. One affected area is called the suprachiasmatic nucleus (SCN), which is responsible for regulating your circadian rhythm, the internal clock that keeps you going to bed and waking up at the same times.
"If you expose yourself to blue light at night, what it can do is shift your clock later," Dr. Wu told POPSUGAR. "It would make you want to go to bed later and then wake up later, which obviously is not ideal for lots of working people." In other words, if you're habitually on your phone or laptop late at night, it can trick your body into thinking it's daytime, keeping you alert and awake when you'd usually start to get sleepy.
"Generally, this is not likely to happen after just one night," said Luis Buenaver, PhD, an assistant professor and director of the Behavioral Sleep Medicine Program at Johns Hopkins's department of psychiatry and behavioral sciences. "But [it] may become an issue after several nights or if it becomes a bad habit."
Blue Light Suppresses Melatonin
Relatedly, melatonin is a hormone that regulates your circadian rhythm. Blue light actually can neutralize the effects of your naturally occurring melatonin, which is "usually secreted about two hours prior to one's habitual bedtime," Dr. Buenaver explained. Too much exposure to blue light can throw off that routine and keep your brain on high alert, making it difficult to fall asleep or sleep soundly once you do drift off.
Blue Light Makes You Feel More Awake
On top of disrupting your circadian rhythm and melatonin production, blue light also directly stimulates the part of your brain that makes you feel awake, Dr. Wu said. That can be a good thing during the day, but "it's not something you want when you're trying to go to bed," he explained.
That's especially important because, even beyond blue light, using your phone or computer before bed will naturally make you feel more alert. If you're reading or watching something that gets you worked up in some way, it's going to be hard to drift off. "You get either excited or upset, and that's not conducive to sleep," Dr. Wu said. When you put together that natural stimulation with the physical effects of blue light on your brain, hormones, and circadian rhythm, you get a combination that's highly likely to disrupt your sleep.
How Can I Stop Blue Light From Hurting My Sleep?
Dr. Wu and Dr. Buenaver suggested a few ways to deal with the sleep issues created by blue light. If you find yourself mindlessly scrolling Instagram or clicking yet another video as it gets closer to bedtime, try a few of these techniques to keep your sleep cycle on track:
- Enable your device's "night mode" function. Your phone or laptop's "night mode" or "dark mode" filters out the blue light from your screen. "It makes your screen look kind of orange-ish. Make sure to enable that," Dr. Wu said, if you're going to looking at your screen close to bedtime.
- Use blue-light-filtering glasses. If your screen doesn't have a night mode function, both doctors said that blue-light-filtering glasses work in the same way. Here are 10 blue-light glasses you can try.
- Dim any ambient lighting. Since regular light exposure can also suppress melatonin, Dr. Wu recommended dimming your overhead lights more and more as you get closer to bedtime. This might mean moving from the well-lit living room to your darker bedroom, or switching from an overhead light to a smaller reading light. This can help bring your circadian rhythm back on track.
- Put down your phone or computer at least 30 minutes before bed. This is the hardest one, we know. "Everyone's always connected to their devices," Dr. Wu said. "But usually we recommend at least a 30-minute or one-hour wind-down period, if possible." Dr. Buenaver recommended trying for a two-hour window — more of a challenge, but something you could work your way up to in time.