Why Does Blue Light Negatively Affect Sleep?
Blue light is part of modern life, built into our screens and home lighting. People take in large amounts of blue light every day, and that can have negative health effects. This article is about blue light: what is blue light, health effects of blue light, how blue light can disrupt circadian rhythms and cause sleep problems, and alternatives to blue light.
What is Blue Light?
Light is electromagnetic radiation with a specific color and frequency, or wavelength. The full spectrum of light (also called the electromagnetic spectrum) includes numerous wavelengths of light with different frequencies and colors, some of which are visible to the human eye, like blue light. Not all light is the same: different wavelengths and colors of light have different physiological impacts on the body. We’ll explain some of the health effects of blue light below. To read more about the basics of light, check out this post.
Blue light is a naturally occurring part of sunlight, in the 450-485 nm range on the visible spectrum. Blue light is also widely used in modern screen technology, to illuminate our phones, laptops, computer screens, and TVs. When humans absorb blue light as part of daytime sunlight (along with red light, NIR light, and other colors on the spectrum), it can have a positive effect. Blue light from the sun can help you stay alert during the day, and enhance your mood, reaction time, and performance.  It’s also shown to have some positive effects for bacterial acne and teeth whitening.
Unfortunately, many people don’t get outside enough to get consistent doses of natural blue light from the sun. The average American spends over 90% of their time indoors.  That means that the blue light people are exposed to mainly comes from home lighting and screens. An overload of bright blue light, especially at night, can have negative health effects. Blue light at night can disrupt circadian rhythms, limit melatonin production, and make it harder to sleep.[3,4] This is why many people wear blue light blocking glasses, or use alternative lighting sources at night, like softer red light.
Why Does Blue Light Negatively Affect Sleep?
Blue light is one of the shortest, highest-energy wavelengths on the spectrum. It’s commonly isolated and used in artificial lighting and electronics because it’s so bright and energy-efficient. Today’s Home lighting with LEDs or fluorescent bulbs is cheaper than ever, but it produces far more blue light than the incandescent bulbs of the past. Blue light has also been extremely disruptive as the main lighting in our screen technologies. What’s good for lighting and technology isn’t necessarily good for our bodies.
We use devices with blue-lit screens constantly, exposing ourselves to bursts of bright blue light at all hours of the day. Humans have never been able to experience so much blue light before, and it’s having negative consequences for our health and sleep.  If you’re struggling to fall asleep at night, even when you’re tired, your electronics use at night may be a factor.
Blue Light at Night Disrupts Circadian Rhythms and Sleep
Devices that emit blue light, like computers and smartphones, can disrupt your circadian rhythms and sleep if you use them after dark. Circadian rhythms are the body’s natural, 24-hour cycles of sleeping, waking, digesting, etc. They’re closely tied to the earth’s rotation and night/day cycles, but that can get thrown out of whack with too much blue light at night. The blue wavelengths emitted by devices are so bright, they can actually trick your brain into thinking it’s daytime. 
Clinical studies are showing that blue light at night interferes with your brain’s natural sleep-wake cycle. [4,5] Blue light has a big effect on our suprachiasmatic nucleus (SCN), the part of your hypothalamus that acts as the body’s master alarm clock. [6,7] The brain interprets light as a signal of when to be awake and asleep. When you take in natural sunlight during the day, the brain recognizes blue light and knows it’s time to be up and alert. But it has a similar reaction at night with artificial blue light, and that can wreak havoc on your sleep.
When the brain receives an overload of bright blue light after dark, your body gets the false impression it’s earlier in the day. Instead of winding down to sleep, your brain and body gear up to be active. Your SCN doesn’t know that you have to wake up early for work. Your brain acts like it’s noon when you stare at a bright blue screen in bed at night before trying to go to sleep. [6,7]
Blue Light Inhibits Melatonin Production and Makes it Harder to Fall Asleep
One of the main ways blue light exposure disrupts sleep is through the inhibition of melatonin hormone. After the sun goes down, your body naturally increases the production of melatonin, which helps you fall asleep. Blue light has the opposite effect. It limits melatonin production, which makes it harder to fall asleep and stay asleep.  When you use bright electronics at night, you are actually limiting your brain’s ability to produce your most important sleeping hormones. For more on the science of light and sleep, check out this post.
Weight Fluctuation: Digestion and metabolism is a circadian rhythm just like our sleep cycle. Changes to our circadian rhythms and sleep from blue light also has a disruptive effect on our body’s ability to process food and burn fat.  This can lead to weight fluctuations. Check out this article for more on light, sleep, and weight.
How to Counteract Blue Light Sleep Problems
With our modern lifestyles, it’s almost impossible to avoid blue light. There are good ways to reduce and limit your artificial blue light intake, so you can maintain your circadian rhythms and sleep cycle. For starters, be aware of your screen time and blue light intake so you can try to limit it,  especially after the sun goes down. Most smartphones have “screen time” features in their settings that can help you get an idea of how much you’re on your phone each day. Here are some other tips for counteracting blue light and sleeping better:
Get Outside and Active During the Daytime: The best way to counteract harmful blue light intake is to receive healthy light from the sun during the day. Full spectrum light from the sun has a wide range of health benefits, like improved mood, energy, productivity, and better sleep at night.  Our bodies are designed to be outside and active when it’s light out. Getting outside and moving in the daytime helps your brain and body align your circadian rhythms with the cycles of the earth. Natural light exposure is also crucial for our sleep hormone production. 
Avoid Blue Light Before Bed: The less blue light you’re exposed to after dark, the better for your sleep. Giving your brain and body time to wind down in lower light is a more relaxing, natural transition to the sleep phase of the day. As a general rule, it’s best to avoid blue light for a solid 2 - 3 hours before you go to sleep. If that’s difficult, at least try to limit screen use in bed. If you watch TV or look at your phone or computer in bed, try reading or relaxing instead. Give your brain time to prepare for sleep before you close your eyes. You can read more about light and sleep here.
Blue Blockers & Night Modes: More people are wearing types of glasses designed to block blue light from screens and other sources. In addition to blue blockers, it can help to use nighttime modes on devices  that reduce the brightness and color of the screen.
Red Light at Night: Red light, like blue light, is a part of natural sunlight. It has much less energy than blue light, and a lower color temperature. That makes red light ideal for nighttime lighting. Red light is softer than blue light. When you light your home with red light at night, you can still see and do things, but it’s less bright for your eyes and brain, and won’t interrupt your circadian rhythm or melatonin production in the same way [11,12].
Light Therapy: In addition to limiting blue light, you need to get healthy light every day. Getting outside is ideal, but not possible for everyone with jobs, kids, and schedules. Light therapy is a way to get healthy wavelengths of red and near-infrared (NIR) light in your home, no matter the weather or time of year. Simple treatments with a high-quality device like a Joovv take just 10-20 minutes, and support a healthy, balanced lifestyle. Learn more about the science of light therapy here and see how wavelengths of red and NIR light affect the body at the cellular level.
Joovv’s Ambient Mode Supports Sleep
Ambient Mode is a setting on Joovv’s light therapy devices that’s designed to support healthier light use and better sleep. Ambient Mode delivers low intensity red light for lighting your home at night, as an alternative to bright blue light. Ambient Mode allows you to use your Joovv as a regular nighttime red light. When you use Ambient Mode to light a room, you can still see and read, but your body and brain aren’t taking in as much blue or white light from traditional light fixtures and screens. This helps smooth the transition into sleep without affecting melatonin levels. Ambient Mode is also a good way to transition into your day in the morning, after you wake up.
Conclusion: Limit Blue Light at Night for Healthy Sleep
Blue light is a natural part of sunlight, but it’s also used to illuminate our screens and homes, and can have a negative effect on sleep and circadian rhythms. Taking in bright blue light at night can limit melatonin production and make it harder to fall asleep. Limiting blue light after dark and using a nighttime lighting alternative like red light can help you transition into sleep and stay asleep.
Sources and References:
 Münch M, Linhart F, et al. Effects of prior light exposure on early evening performance, subjective sleepiness, and hormonal secretion. Behavioral Neuroscience. 2012 Feb.
 Klepeis NE, Nelson WC, Ott WR, et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. J Expo Anal Environ Epidemiol. 2001 May.
 David C. Holzman. What’s in a Color? The Unique Human Health Effects of Blue Light. Environmental Health Perspectives. 2010 Jan.
 Nazish Rafique, Lubna Ibrahim Al-Asoom, Ahmed Abdulrahman Alsunni, Farhat Nadeem Saudagar, Latifah Almulhim, Gaeda Alkaltham. Effects of Mobile Use on Subjective Sleep Quality. Nat Sci Sleep. 2020 Jun 23.
 Duffy J, Czeisler C. Effect of Light on Human Circadian Physiology. Sleep Medicine Clinics. 2009 Jun.
 Moore, R. “Suprachiasmatic nucleus in sleep-wake regulation” Sleep Med. 2007 Dec.
 Norihiro Nagai, Masahiko Ayaki, et al. Suppression of Blue Light at Night Ameliorates Metabolic Abnormalities by Controlling Circadian Rhythms. Invest Ophthalmol Vis Sci. 2019 Sep.
 Jorge A Calvo-Sanz, Carlos E Tapia-Ayuga. Blue light emission spectra on popular mobile devices: The extent of user protection against melatonin suppression by built-in screen technology and light filtering software systems. Chronobiol Int. 2020 Jul;37(7):1016-1022
 Book: Satchin Panda, PhD. The Circadian Code: lose weight, supercharge your energy, and transform your health from morning to midnight. Rodale Books. Jun 12, 2018 | ISBN 9781635652437
 Mead N. Benefits of Sunlight: A Bright Spot for Human Health. Environmental Health Perspectives. 2008 Apr.
 Mariana G Figueiro, Levent Sahin, Charles Roohan, Michael Kalsher, Barbara Plitnick, and Mark S Rea. Effects of red light on sleep inertia. Nat Sci Sleep. 2019.
 Mariana G Figueiro, Levent Sahin, Brittany Wood, Barbara Plitnick. Light at Night and Measures of Alertness and Performance: Implications for Shift Workers. Biol Res Nurs. 2016 Jan.