Photo by Alexander Jawfox on Unsplash
What’s the last thing you do before bed every night? Whether it’s scrolling through social media or putting on a show to fall asleep to, many of us find ourselves glued to one LED screen or another after dark. Yet in the grand scheme of things, this is relatively new exposure for humans — after all, it wasn’t until the 21st century that LED technology became popular.
As science has come to learn more about the light emitted by these devices, we’re finding out that these modern habits may have consequences for our health. In this article, we’ll illuminate why that is, explaining the effects of the light, what we mean when we say blue light, and how you can minimize its negative impacts.
What is blue light?
While your high school physics class may feel like a distant blur, you may remember learning that light travels in electromagnetic waves, each of which has high points known as crests. If it’s all still fresh, you may even recall that the distance between these crests is called the wavelength. When it comes to light, or really any electromagnetic wave, it’s all about the wavelength.
Of the waves that make up the visible light spectrum (the small portion of the electromagnetic spectrum that we can actually see), blue light has one of the shortest wavelengths, while red light has the longest. So when we talk about blue light, we’re not necessarily talking about a specific color of light, but rather, a specific wavelength.
Take the light emitted by the sun. It emits a specific wavelength on the electromagnetic spectrum, but that doesn’t shroud us in blue or turn the objects it touches blue. This same blue wavelength is emitted by LED (light-emitting diode) lights, which make up the screens of several of the devices we depend on day in and day out.
What are sources of blue light?
- The sun
- Fluorescent lights
- LED lights (including energy-efficient light-bulbs)
Why is blue light bad?
To say that blue light is bad is actually an oversimplification. Many of our physiological processes depend on blue light — especially our circadian rhythms. These rhythms are the 24-hour cycles that run our internal clocks and help the body carry out functions and processes that are crucial to our wellbeing. There are actually several circadian rhythms, but the most familiar is the sleep-wake cycle. The blue light emitted by the sun governs this cycle, telling your body when to be awake and alert or when it’s time to go to bed.
What makes the blue light emitted by screen-based devices harmful isn’t necessarily the light they emit. Rather, it’s the misalignment created in our circadian rhythms when we’re exposed to blue light outside of the hours of exposure that have been natural to humans for millennia. Simply put, when the sun goes down, our bodies take the absence of blue light as a signal to launch a plethora of physiological processes. Exposure to blue light after sunset, especially at bedtime, disrupts those processes, which can have a number of negative effects on health.
How does blue light affect you?
Blue light affects sleep.
It’s no secret that good sleep is one of the most important factors in human health — especially for people with conditions such as migraine, for whom too little sleep can trigger a debilitating attack. Research has shown that using blue-light-emitting devices before bedtime prevents you from falling asleep. Considering that prolonged exposure to blue-wavelength light alerts the body, this isn’t all too surprising.
A 2005 study shows how blue light affects sleep. Researchers found that five hours of evening exposure to an LED-backlit computer suppresses melatonin secretion and decreased sleepiness when compared to five hours of exposure to a non-LED screen. Meanwhile, a separate study found that wearing blue-light-blocking lenses before bedtime increased the total time, soundness, and quality of sleep in participants with insomnia.
Blue light is damaging to the eyes.
A review of medical literature published in the International Journal of Ophthalmology found evidence to support that blue-wavelength light damages the human eye — specifically in regards to the cornea, lens, and retina. It not only causes inflammation of cells in the cornea and oxidative damage that can lead to dry eye, but it also penetrates through the lens to the retina. This in turn can lead to retinal damage such as degeneration, stress injury, and destruction of the blood retinal barrier.
But don’t worry! We’ll get into how to protect eyes from blue light in just a bit.
Blue light causes skin to age more rapidly.
In a time when so many jobs keep us indoors and in front of a screen, humans are exposed to inadequate levels of blue light during the day and overexposed to blue-wavelength light at night. Even when the period of exposure is relatively short, after-hours exposure to blue light can cause oxidative stress in skin cells, which leads to premature aging. This ties directly back to our circadian rhythms, because in a natural 24-hour cycle, our skin is focused on protection during the day and regeneration at night.
But what does blue light do to skin, exactly? A recent paper shows that exposure to blue light at night actually tricks skin cells, which can directly perceive the presence of light, into thinking it’s daytime. As a result, our skin switches from a state of regeneration to protection, which in turn leads to DNA damage and inflammation that increases skin damage and accelerates aging.
Blue light exacerbates photophobia.
In 2016, Dr. Rami Burstein of Harvard University published groundbreaking research illustrating how different wavelengths of light affect light sensitivity in migraine patients. By exposing participants to wavelengths of white (regular room light), blue, green, amber, and red lights during a migraine, he and his team found that blue- and red lights exacerbate migraine headache - a phenomenon known as photophobia - more than any other color of light. Interestingly, a very narrow band of green light did exactly the opposite: it reduced the headache intensity caused by light and was often described as having profound soothing effects.
Blue light contributes to age-related disorders.
Misalignment of human circadian rhythms is believed to play a role in the development of numerous disorders associated with aging — including depression, diabetes, hypertension, and obesity. By limiting blue-light exposure to optimal times and intensities, it may be possible to limit the circadian disruption that impacts health and potentially contributes to the development of disorders such as those listed above.
Blue light may accelerate neurodegeneration.
A 2019 study sought to understand the degenerative effects of blue light on adult flies by exposing three different groups of flies to different lighting conditions. One group was maintained in daily cycles of 12 hours of blue LED light and 12 hours of darkness, while two others were kept in either constant darkness or white light with blue wavelengths blocked. Of the three groups, the aging phenotypes of flies exposed to blue light were most accelerated, causing brain neurodegeneration.
Blue light may increase risk of certain cancers.
A large case-control study published in 2018 suggests that exposure to blue light at night may be associated with hormone-dependent cancers. The study followed thousands of participants in Spain, tracking the correlation of light exposure at night to the development of breast and prostate cancer. Researchers found that both types of cancer were associated with high exposure to the blue-enriched light spectrum at night.
Blue light is also a credible risk factor for the development of uveal melanoma in the eye, according to a separate study published in 2015.
Here’s how you can protect yourself.
Again, when we talk about protecting yourself from blue light, we’re mainly referring to blue light exposure at night from artificial sources, as this falls outside of our natural circadian rhythms. The simplest way to avoid blue light at night is by turning off sources of blue-wavelength LED light at least 2 hours before bedtime. However, in a time when work and entertainment may heavily rely on blue-light-emitting devices, it’s easier said than done.
Luckily, by using the following tips, it’s possible to limit that exposure and minimize the adverse effects we just discussed.
Turn it off way before bed.
Turning electronics off two to three hours before bedtime can make a monumental difference in your quality of sleep and keep your circadian rhythms in alignment. Consider keeping your smartphone in another room while sleeping, or flip it over so that the screen isn’t facing up on your nightstand.
Try blue-light-blocking lenses.
Blue light-blocking lenses have become widely available and are easily accessible — even if you wear prescription lenses. Consider wearing these lenses when you’re using devices with LED screens to protect your eyes from blue-wavelength light.
Not all sources of light are blue. Turning to green-wavelength light, such as the light emitted by the Allay Lamp, can offer a source of illumination for reading and other activities without the damaging effects of blue light. Portable, chargeable, and dimmable, the Allay Lamp or Desk Light makes for a great bedside light that you can turn to in the hour(s) before bed. They both work great for reading and after-hours work as well.
Try an app that blocks blue light.
There are several apps available on both smartphones and computers that block blue-wavelength light. Consider downloading these via the App Store (Apple devices) or Google Play Store (Android devices) and using them after the sun goes down.
Can you dim it?
The higher the intensity of blue light, the more disruptive it is to our eyes and circadian rhythms. Luckily, most devices allow you to easily dim your screen while using them, as do dimmable LED light bulbs. If you can’t avoid blue light at night, simply turning down the light source a bit can still make a big difference.
Black out your bedroom.
From alarm clocks to air purifiers, you likely have some subtle source of light in your bedroom at night — even if it’s just artificial light from street lamps making its way in through your window. Consider putting a piece of tape over the light on your air purifier, putting black-out curtains in your bedroom, or even simply wearing an eye mask to protect yourself from these light sources that disrupt your sleep.
Ready to trade in the blue?
Looking for more Light Reading from our team?
- Green Light Therapy: Everything You Need to Know
- The Science Behind The Allay Lamp
- Understanding Photophobia: Why Light Sensitivity Happens & How to Treat It