What is Blue Light and How Does it Affect Sleep?

What is blue light? - blue at night and sleep

Unless you’re living under a rock, it’s impossible to go along with the day without staring at a scree.n

You wake up to your phone’s alarm, sometimes even fumbling to snooze it a dozen times. At work, you spend a couple of hours in front of a computer. You might also get your daily dose of evening news from the television.

Artificial lighting seems to be inalienable from our everyday routine, but have you ever wondered what prolonged exposure can do to your body?

Bad news for people who can’t live without their gadgets, Harvard Health Publishing cautioned that blue light from screens could sabotage your sleep patterns and even your health real bad. 

If you spend almost half of your day basking your eyes in blue light, you are at risk of sleeping disorders, which are considered highways to obesity, diabetes, cancer, and heart disease.

And so in this guide, let’s break down the science behind blue light and its impact on our circadian rhythm

You probably had a mini heart attack after reading that list of health complications (you’re reading this now on a screen after all), so we threw in tips on how to protect yourself from blue light too.

Blue light at night

What is blue light?

You’ve learned in school that light comes in varied colors and wavelengths. 

Basically, blue light already describes itself – light in the form of blue wavelengths.

Different types of light produce different effects. Ultraviolet light and its skin-damaging properties might already be familiar. Meanwhile, blue light’s specialty is keeping us energized during the daytime. It’s a proven natural booster for our reaction times, attention, and mood.

Our eyes pretty much soak up almost all blue light we’re exposed to, which quickly passes through the retina. Usually, it helps the brain process light into understandable images.

Where does blue light come from?

Blue light is mainly supplied by the sun, that’s why we often feel refreshed and ready to get on with the day after basking in morning rays.

However, artificial light kicks in when Mr. sun goes down, prolonging our exposure to blue light. Among the most common sources of blue light indoors are:

Electronic devices

Blue light phone screen at night

These include smartphones, tablets, televisions, gaming systems, and computer monitors. Although these gadgets appear to emit white light, measuring its wavelengths (400 to 490 nanometers) will reveal that it’s blue.

The average American spends about seven hours a day using electronic devices, and that’s quite a lot. 9 out of 10 even confessed that using a gadget is a part of their bedtime routine. No wonder many of us have to count a million sheep just to get to dreamland.

Light bulbs

red light at night

This one’s quite the irony. It seems like our quest for environmentally friendly and energy-efficient lighting came at the expense of people’s health. 

Switching to LED lighting may save you a few bucks on your electricity bill, but expect to get a higher dose of blue light. 

In contrast, fluorescent bulbs have coatings that produce a warmer toned light with less blue wavelengths but they flicker in an awful way.

Your best options in this day and age are the good old incandescent lights or a true “red” or infrared bulb. These emit the least blue light.

How does blue light affect sleep?

There are two ways through which blue light can stop you from getting a good night’s sleep. It sabotages your body’s production of sleep-inducing hormones, and it also throws you off your normal biological clock. Let’s explore how exactly this works.

Sleepy Bed

Blue light and melatonin production

In the same way that our bitter folks devalue love as a mere cocktail of chemicals in our brain, it’s the science of hormones that also determine our ability to sleep.

By producing melatonin, your brain signals the body that it’s time to rest. Sleep patterns are usually triggered by darkness, so that’s why we have the natural tendency to rise along with the sun and feel sleepy and tired as it sets.

Apparently, blue light can block off your supply of melatonin. Sure, your phone seems to be a puny light source as compared with the sun, but it’s powerful enough to disrupt your sleep cycle.

Here’s the science behind that: any light can disrupt melatonin production, but exposure to blue light at night can do so more strongly. 

Our friends at Harvard had this study that compared blue light to green light. After 6.5 hours of tests, the subject exposed to blue light had his melatonin production suppressed (3 hours) for twice as much as the impact of green light (1.5 hours).

We’ve also mentioned earlier that our eyes suck at filtering blue light. When the melanopsin receptors catch blue light, it’s pretty much given an all-access pass towards a late-night party in your brain.

Blue light and the circadian rhythm

Light is among the most potent elements that can tweak your body clock. Your circadian rhythm, which calls the shots in your sleep cycle, feeding patterns, and many other physiological processes, is affected by how much light and darkness you are exposed to.

Similar to how melatonin production works, the default setting of your circadian rhythm is guided by the sun’s natural light. Your brain designs your sleeping habits in accordance with whether it’s bright or dark outside. 

In the morning, sensing light helps your brain signal the production of cortisol hormones that boots your body up. 

As the moon calls dibs on the sky, the brain adjusts your body temperature to drop in preparation for sleep.

When you add blue light to the equation, your circadian rhythm becomes all messed up and confused. Your day-long exposure to light makes your brain clueless on when it’s supposed to get you ready for rest.

Is exposure to blue light bad for Your health?

From poor eyesight to fatal illnesses, prolonged exposure to blue light can cause many health problems. This list might make you think twice if binge-watching Netflix or hours of mindless scrolling on your Twitter feed is worth the trouble.

blue light computer


It’s not just your shoulders and back that can fall victim to physical discomfort due to hours of work with electronic devices. Excessive blue light exposure can also stress your eyes out badly. Ever feel like your eyes are so dry and sore to the point that your vision is compromised? Yup, that’s eye strain. 

Macular Degeneration

Eye irritation already seems like a hassle, and we hope you won’t wait ‘til you catch serious complications affecting your vision. Blue light increases people’s risk of macular degeneration by damaging the retina. When left unchecked, this problem can elevate to the permanent loss of your sense of sight.

Diabetes and obesity

Electronic devices snatch precious time that could be better spent in the gym. Even worse, the blue light it emits can also make you more vulnerable to diabetes and obesity. Take it from a Harvard study who tried to alter the circadian rhythm of 10 subjects. The results? Increased blood sugar level coupled with decreased levels of leptin, a hormone that triggers you to feel full after a meal.

Other fatal illnesses

It has yet to be proven that exposure to blue light at night directly causes cancer and cardiovascular diseases. However, studies have long related unhealthy circadian rhythms and disrupted melatonin production with these fatal illnesses.

How can I prevent sleep problems because of blue light?

Thought twice about the unhealthy hours you spend on your gadgets? Here’s how you can protect yourself from the blue light-induced health complications that we’ve discussed.

Stay away from any electronic device before bedtime

The most basic solution is just to ditch electronic devices at night. Save all your computer-related work for the day! But if that’s quite impossible, we highly recommend avoiding bright screens two to three hours before sleeping. You can set the alarm to remind you to store all gadgets far from your bed, so you can stay clear of any temptation to use them. 

Use An APP or Dim brightness

On your phone and computers, you can use iris tech or f.lux . Most devices have their own capability as well, but something like iris does more than just block blue light. Lower brightness does sometimes mean lower blue light but the filtering applications will help remove the blue wavelengths. Ensure you at the least set your devices on night or dark mode. This way, your gadgets will less likely disrupt your melatonin production.

Go for smaller screens

The bigger your electronic device’s screen is, the higher amount of blue light you are exposed to. Try to develop a preference for gadgets with smaller displays. However, we know you can’t just throw your 50-inch TV down the bin. For a quick fix, view digital screens from longer distances so your eyes won’t catch as much blue light.

Switch to warm-toned bulbs

Apart from your gadgets, we’ve mentioned that indoor lighting also produces blue light. For a sleep-friendly ambiance in your home, using warm-toned bulbs might be a good alternative. Among all kinds of wavelengths, red lights cause the least disruption on your circadian rhythm. Got some extra bucks? You could also invest in “smart lights” that can be programmed to emit warmer shades during the night. 

Lighting is complicated, if ever in doubt and you need a light that is not red at night, use a candle! Or in a pinch, purchase incandescents. We will cover lighting in more depth on a later date.

Invest in blue light glasses

For night owls, you might want to seek the help of protective eyewear designed to block blue light. These glasses can make staring at screens more guilt-free, thanks to its anti-reflective filters and coatings. 

Want proof? A study from the University of Toronto involved an experiment where people wearing blue light glasses were exposed to bright indoor light. Findings have shown that these subject’s melatonin levels were the same as those who were exposed to dim light without any protective eyewear. 

Use our guide here to find the best!

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