How Does Blue Light Affect Sleep?

December 1, 2023 · John Gallagher

How Does Blue Light Affect the Sleep-Wake Cycle? 4 Things to Know.

All screens emit blue light — the highest-energy wavelength that helps reinforce the sleep-wake cycle. The sun is the world’s largest source of blue light, though most people are also frequently exposed to blue light through phone, television, and computer screens.

During the day, appropriate exposure to blue light does little to damage health. Most people are naturally exposed to blue light on a regular basis, whether you’re answering a phone call or walking through a park. In the morning and early afternoon hours, blue light exposure can even improve your mood and keep you alert — like a cup of coffee, but without the negative effects that caffeine can have on sleep.

However, blue light exposure during the evening can compromise your sleep-wake cycle. It will suppress necessary sleep hormones and prevent your body from winding down. This effect is particularly prevalent for the 71% of people who admit to sleeping with their phones. Your brain will believe it’s still daytime, keeping it from guiding the body into a peaceful slumber.

What is Blue Light?

Blue light is the shortest wavelength that we can see with the naked eye. An estimated 33% of all light is blue light, helping your body distinguish between daytime and nighttime hours. LED devices like flat-screen televisions and laptops emit particularly high volumes of blue light, as valuable during the day as it is damaging in the evening.

Only a small fraction of blue light exposure comes from screens. However, the human eye is not designed to block blue light. This means that nearly all blue light reaches our retinas. Over time, prolonged or poorly-timed blue light exposure can lead to vision problems like cataracts or age-related macular degeneration. The same exposure can impact sleep in powerful ways.

How Does Blue Light Impact Sleep?

Excessive exposure to blue light has several damaging consequences on sleep. It can throw off your circadian rhythm, delay sleep onset, damage sleep hygiene, and suppress your body’s melatonin production processes. Blue light will impair your ability to fall asleep, stay asleep, and reduce overall sleep quality on a nightly basis.

1. Blue Light Delays Sleep Onset.

On average, it takes between 10 and 20 minutes to fall asleep. However, blue light can disrupt this process, delaying sleep onset and keeping you awake far longer than you intended.

When you sleep, your brain is hard at work on several important priorities. It helps to heal your body from any injuries, register memories, remove toxins, and even process the day’s emotional experiences. During the evening, your brain wants to begin winding down and preparing for these steps. Blue light directly delays the onset of these sleep stages, tricking your brain into believing it’s still daytime. 

Your brain confuses phone-emitted blue light with blue light from the sun, preventing you from falling asleep at a preferred time. Melatonin production is also suppressed, making it more difficult to calm internal systems like respiration and digestion.

2. Blue Light Suppresses Melatonin Production.

One of the main ways blue light affects sleep is by limiting melatonin production. Melatonin is widely regarded as the “sleep hormone”, one that plays an important role in protecting your circadian rhythm. Melatonin also helps your brain recognize the light-dark cycle, prompting your body to automatically wind down as evening sets in.

Particularly at night, blue light impedes melatonin production. It signals to the body that it’s not yet time for sleep. Blue light stimulates your eyes’ photoreceptors, which are responsible for telling the brain how the eyes perceive images. Without melatonin, your sleep might feel fragmented or incomplete. You may also experience frequent wake episodes during the night, without much restorative deep sleep in between.

3. Blue Light Disrupts Your Circadian Rhythm.

Your circadian rhythm, also known as your sleep-wake cycle, is a powerful process in the body. It helps outline how your body functions when asleep and awake. It also defines your level of alertness and governs hormone production.

During the morning and early afternoon, exposure to blue light actually regulates your circadian rhythm. It synchronizes important internal processes like digestion while helping your body respond to daytime hours with an appropriate level of alertness and action.

Continued blue light exposure in the evening can damage your sleep-wake cycle.  Lack of melatonin production, combined with a confused brain, means more difficulty in falling asleep. A disrupted circadian rhythm can also throw off important priorities that your body typically handles while you sleep.

4. Blue Light Damages Sleep Hygiene.

Sleep hygiene is a group of habits that promote healthy, restful sleep. For best sleep results, many people follow a sleep hygiene checklist that includes items like brushing teeth, stretching, and dimming the lights. They might also practice sleep journaling or meditation to relieve stress before turning in for bed.

Blue light damages sleep hygiene by delaying its final stage: sleep itself. Sleep hygiene is all about creating a comfortable sleep environment, one that’s free from distractions or factors that might impair sleep. Those factors include blue light, which can single-handedly delay sleep onset and hormone production.

How Do I Limit the Effects of Blue Light on Sleep?

Blue light doesn’t need to prevent restful sleep in your household. There are several things you can do to limit its effects, including turning your devices to “Night Mode”. These modes emit less blue light, helping to guide your body toward relaxation. Even better, stop all device use — including phones, computers, tablets, and televisions — one full hour before you plan on heading to bed.

Here are some more things you can do keep blue light from impacting your sleep:

  • Use a screen protector on your device: many screen protectors include filters that at least partially block blue light. Find a thin screen protector with a film that maintains screen clarity while blocking a healthy percentage of blue light exposure.
  • Incorporate dim bedroom lighting: Dim lighting is a further signal to your brain that it’s time for sleep. Install dim lighting, or a dimmer that can lower bedroom light volume, to further reduce emitted blue light around your bed.
  • Make your bed a device-free zone: The best way to limit the effects of blue light on sleep is to eliminate blue light during evening hours. Keep devices out of your bed to reduce any blue light exposure in the minutes before sleep.
  • Establish sleep accountability: Find a partner to join you in blue-light-free sleep. This could be someone who sleeps next to you or in your home. Provide them with a list of your sleep goals and give them the freedom to keep you accountable for any late-night device use.

These strategies all require a common ingredient: your participation. Even the best intentions can’t survive if you continue to bring your phone into bed with you. Power off your phone, leave it in a safe place, and embrace the rest you deserve after a productive day.

How Else Can I Improve Sleep Quality?

Reducing blue light isn’t the only way to improve sleep quality in your home. You can also avoid heavy meals with ingredients that might cause sleep-delaying indigestion. It's also important to manage bedroom noise, perhaps with earplugs or a sleep machine that emits white noise. Since daytime naps can delay evening sleep, we suggest an energy-boosting activity like physical exercise.

Getting the right mattress is another hurdle on your journey toward better sleep. The right mattress is a critical ingredient in sleep hygiene, and helps keep sleep a priority no matter your other responsibilities during the day. At Mattress Warehouse, we understand that different people have different definitions of ideal sleep. That’s why we’ve done the hard part for you, through a quick quiz that analyzes your sleep patterns and makes personalized recommendations on the right mattress. BedMATCH is free, and only takes a few minutes to complete. The result is instantly-improved sleep, which belongs at the top of everyone's to-do-list — no matter the type of mattress you need.