Here’s How Blue Light Really Affects Your Sleep & Attention

by JR Thorpe
 A woman uses her phone in bed first thing in the morning. Blue light's effects on sleep are variabl...
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As tempting as it is to curl up with your phone before you go to bed, research has suggested that blue light, which is emitted by electronic devices, can disrupt our sleep patterns. But it's more complicated than researchers once thought: blue light's effects on sleep have to do with particular parts of the brain, the eye, and the body's circadian clock. And it turns out that the way blue light interacts with these parts of your body can also have a positive effect on your attention and memory. If your mom insists you wear your blue light glasses when you're looking on your phone, you might want to take that with a grain of salt.

Blue light, sleep expert Dr. Michael Breus Ph.D. tells Bustle, is the term for the wavelength of light between 460-490 nm (nanometers). It's the shortest wavelength of light, and we encounter it daily — but it's particularly prevalent in electronic devices that don't have light adjustments fitted. There's some evidence that it can be stimulating, and thus has the potential to mess up our body's internal clock. You shouldn't throw out all your blue light devices, though; some scientists now think that the presence of blue light isn't all that harmful, and may even have positive effects on sleep and wakefulness when used in the right ways. Here's the current science on blue light and sleep.


It's Thought To Interfere With Melatonin Production

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There's a lot of evidence that exposure to blue light affects the brain's melatonin production. Melatonin is a hormone that manages the body's sleep reactions. "It's like the key that starts the engine for sleep," Dr. Breus tells Bustle. Melatonin doesn't make us sleep; instead, it's like a signal to the brain to begin the process of entering a sleepy state. This is why it's marketed as a way to readjust sleep patterns after long flights, instead of as a sleep aid that induces immediate slumber.

Dr. Timothy Brown Ph.D., a researcher on eyes and visual perception at the University of Manchester, tells Bustle that there's a lot of research that shows light has immediate effects on our melatonin levels. Light suppresses melatonin because they signal that it's time to be awake, which is why it's important to try to sleep in dark rooms and exclude light. Blue light, some scientists suggest, might be particularly damaging to melatonin production at night. "Blue light at night will not allow for proper melatonin production or release, or at the very least will delay it," Dr. Breus says.


The Blueness Of The Light Doesn't Matter As Much As You Think

Scientists have thought for some time that it's the color of blue light in particular that alters melatonin levels in the brain. Dr. Breus explains that blue light affects certain proteins in the eye, known as melanopsin cells, that send messages to our brain about melatonin production. However, the process is more complicated than we thought.

Research published by Dr. Brown in Current Biology in late 2019 found that the color of the light we see at night might not matter as much as we thought. In other words, blue light might not be the big bad sleep-enemy we thought. The melanopsin cells in the eye, Dr. Brown tells Bustle, can absorb more light at low wavelengths — like blue light — than other kinds of light. However, it can't actually detect the color of the light itself.

Dr. Brown's team experimented with mice and found that blue light actually has a weaker effect on melanopsin proteins than yellow light that was equally bright. The real problem appears to be the brightness of the light, not necessarily its color. "If one wants to make it easier to sleep at night and wake up early, then use bright light in the morning and as dim as practically possible in the evening," he tells Bustle.


Blue Light Can Help Your Attention

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Blue light has been shown to help attention and wakefulness — and that can be a benefit if you choose to use it in the daytime. Two studies published in 2019 found that short bursts of bright blue light exposure in the morning helped people feel more awake and focussed, and improved cognitive performance. Even half an hour of blue light could produce significant effects on some people. It's likely that this has something to do with our internal body clocks and the signals they received from the light; the brightness of the light may have prompted the brain to adjust its alertness.


It Might Help Repair Your Brain When You Wake

Blue light at night might not be as bad for sleep as we thought, and blue light in the morning might actually help brain repair. That's the conclusion of a 2020 study published in Neurobiology of Disease, which found that people with minor traumatic brain injuries who were exposed to blue light wavelengths in the mornings exhibited better brain processing, and also showed growth in the volume of a brain area called the pulvinar nucleus, which is responsible for visual attention. Healing from minor injuries to the brain is difficult, and sleep definitely plays a role — but this is the first study to show that blue light and its influence on wakefulness can help, too.


Blue light's influence on sleep, the brain and wakefulness may not be as simple as we first thought. Banishing blue light devices may be a good way to help you fall asleep — if only because it stops you scrolling Instagram past midnight.


Studies cited:

Kalmbach, D. A., Conroy, D. A., Falk, H., Rao, V., Roy, D., Peters, M. E., … Korley, F. K. (2018). Poor sleep is linked to impeded recovery from traumatic brain injury. Sleep, 41(10). doi: 10.1093/sleep/zsy147

Killgore, W. D., Vanuk, J. R., Shane, B. R., Weber, M., & Bajaj, S. (2020). A randomized, double-blind, placebo-controlled trial of blue wavelength light exposure on sleep and recovery of brain structure, function, and cognition following mild traumatic brain injury. Neurobiology of Disease, 134, 104679. doi: 10.1016/j.nbd.2019.104679

Morgia, C. L., Carelli, V., & Carbonelli, M. (2018). Melanopsin Retinal Ganglion Cells and Pupil: Clinical Implications for Neuro-Ophthalmology. Frontiers in Neurology, 9. doi: 10.3389/fneur.2018.01047

Mouland, J. W., Martial, F., Watson, A., Lucas, R. J., & Brown, T. M. (2019). Cones Support Alignment to an Inconsistent World by Suppressing Mouse Circadian Responses to the Blue Colors Associated with Twilight. Current Biology, 29(24). doi: 10.1016/j.cub.2019.10.028

Studer, P., Brucker, J. M., Haag, C., Doren, J. V., Moll, G. H., Heinrich, H., & Kratz, O. (2019). Effects of blue- and red-enriched light on attention and sleep in typically developing adolescents. Physiology & Behavior, 199, 11–19. doi: 10.1016/j.physbeh.2018.10.015

Tonetti, L., & Natale, V. (2019). Effects of a single short exposure to blue light on cognitive performance. Chronobiology International, 36(5), 725–732. doi: 10.1080/07420528.2019.1593191

Tähkämö, L., Partonen, T., & Pesonen, A.-K. (2018). Systematic review of light exposure impact on human circadian rhythm. Chronobiology International, 36(2), 151–170. doi: 10.1080/07420528.2018.1527773


Dr. Michael Breus Ph.D., sleep expert

Dr. Timothy Brown Ph.D., researcher at the University of Manchester