How Blue Light Effects Sleep & How to Limit Exposure

June 20, 2024

By now you’re probably aware that using electronics — such as your phone, laptop or tablet — during the hours before going to sleep is not the best habit to fall into, due to how blue light affects your circadian rhythm.

Researchers believe that light exposure at night is part of the reason so many people deal with sleep deprivation and consequences like weight gain, low energy and depressive moods as a result.

Maybe you’re wondering, “What is blue light on my phone exactly?”

Below we’ll discuss how blue light differs from other light wavelengths, the effects it has on your body (both good and bad), and simple ways you can control your exposure.

What Is Blue Light?

Visible blue light is the portion of the visible light spectrum that has the shortest wavelengths and highest energy.

According to All About Vision, “Blue light generally is defined as visible light ranging from 380 to 500 nm. Blue light is sometimes further broken down into blue-violet light (roughly 380 to 450 nm) and blue-turquoise light (roughly 450 to 500 nm).”

What does blue light do?

Because it helps to establish your “biological clock,” it has many different effects on physical and psychological processes — including those that determine alertness, sleep, moods, motivation, memory, appetite, blood sugar regulation and more.

Bright blue light works by stimulating cells in the retina that connect to the hypothalamus, a part of the brain that helps control circadian rhythms and many metabolic/endocrine functions.

Where are you exposed to blue light?

You’re exposed to blue light in many situations, including when you’re both outdoors and indoors. According to the American Academy of Ophthalmology, sources of blue light include:

Sunlight, the main source of this type of light. It’s actually blue light rays scattering that make a cloudless sky appear blue on a sunny day.
Fluorescent and LED bulbs, which help to light your home.
Display screens of electronic devices, including computers, laptops, tablets/notebooks and smartphones. Studies show that for most people, the amount of blue light received from screens is actually small compared to the amount from the sun.
Light therapy boxes used to treat seasonal affective disorder. (There is also red light therapy, green light therapy and sun lamp therapy.)

Effects of Blue Light on Sleep

Writers at Harvard Health Publishing tell us that, “Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness.”

Today, however, most of us are exposed to light (devices and bulbs) right up until the point we go to sleep.

How does blue light affect sleep?

It’s now widely known that spending time on digital devices close to bedtime can disrupt your circadian rhythm, which helps determine when you feel sleepy versus awake.

When your circadian rhythm is thrown out of whack, you may become more susceptible to developing conditions such as diabetes, heart disease and obesity.

There’s evidence that high-energy light exposure at night (once it’s dark outside) suppresses the release of the hormone melatonin, which is the primary hormone that influences circadian rhythms and sleep cycles.

Lower melatonin levels can make it harder to fall and stay asleep, and now emerging studies suggest it may also be linked with other health problems.

How Blue Light Affects the Eyes

Why else is blue light bad for you?

One reason is because it tends to cause “eye strain.”

Staring into the screens of digital devices for long periods causes the eyes to absorb a lot of unfocused light, which leads to squinting, irritation, dryness of the eyes, trouble focusing and what feels like eye fatigue. This is also known as computer vision syndrome.

Some experts are also concerned that frequent exposure to high-energy light may have potential long-term effects of eye health.

How can blue light cause eye damage?

Compared to UV light, human eyes are not nearly as good at blocking blue light. A very high percentage of visible blue light passes through the corneas and lenses of the eyes and reaches the retinas (the inner lining of the back of the eye).

This may lead to damage to the retinas and changes in vision, including a higher risk for macular degeneration.

However, there isn’t concrete evidence that blue light exposure increases the risk of macular degeneration, and eye doctors do not appear to be overly concerned about it right now.

Researchers do note, though, that blue light-emitting devices are relatively new in the grand scheme, and more long-term studies are needed to learn more about their effects.

Other Risks and Side Effects

Aside from concerns about eye damage, too much blue light exposure at night is now linked with disruptions in circadian rhythms, and as mentioned above, this may be a risk for problems, such as:

Blood sugar fluctuations
Obesity/weight gain (due to changes in levels of leptin, a hormone that contributes to fullness)
Diabetes
Cardiovascular problems
Depression
Possibly even cancer
Headaches

Are There Any Blue Light Benefits?

Blue light isn’t inherently bad and in fact is associated with some benefits. While exposure at night can disrupt sleep, exposure during the day is actually important for regulating a number of bodily functions.

For instance, if you’re looking for how to improve memory, blue light may be able to help.

Sunlight exposure, which is the No. 1 way that people are exposed to high-energy visible light, is needed to maintain healthy vitamin D levels and also to regulate our circadian rhythms (the body’s natural wakefulness and sleep cycle) and moods.

Exposure to natural light outdoors has also been shown to increase alertness, protect against depression (specifically seasonal affective disorder, a type of depression that’s related to changes in seasons and lack of sunlight), and help with memory and other cognitive functions.

Because a regulated circadian rhythm is important for getting restorative sleep, there’s also associations between daytime blue light exposure and protection against obesity, diabetes, heart disease and other conditions.

“Light therapy” boxes, which emit bright white and blue light rays, can help treat seasonal affective disorder (SAD) symptoms such as fatigue, weight gain and feelings of worthlessness. Some studies suggest that light therapy boxes used for about 30 minutes daily can even be as effective as antidepressant medications for treating SAD.

There is even some evidence that blue light exposure can boost skin health. For instance, research shows it may help:

How to Limit Exposure

1. Avoid electronic devices close to bedtime

Using your phone, watching TV in close proximity and reading on a tablet before bedtime can disrupt your internal clock, potentially causing sleepless nights and daytime fatigue. It’s recommended by experts that you avoid using electronics two to three hours before going to sleep, or at least use only electronics that have blue light filters enabled.

It’s also smart to limit proximity to screens during the day and the length of time spent looking at them, especially up close without breaks.

2. Filter blue light with glasses and apps

Want to keep using electronics at night, but also to protect your eyes from blue light? The best option is give blue light-blocking technology a try, including blue light glasses and settings on your computer/phone/table that filter light.

In recent years, more and more filtering apps have become available for smartphones, tablets and computer screens that prevent significant amounts of blue light from being emitted from these devices.

How do blue light glasses work? They contain a coating that blocks bright light wavelengths from reaching your eyes.

Some are amber or yellow-tinted lenses, and many are available without prescription. They can also help increase contrast when you’re working on devices for long periods, which can improve comfort and reduce eye strain.

Talk to your doctor about which type of glasses/lenses with filters will be best for you. There are now a number of options available depending on whether you normally wear lenses/glasses or not, such as:

Single vision lenses that allow you to view a wider visual field, such as your entire computer screen.
Glasses with special glare-reducing, anti-reflective coatings that block high-energy light from both the sun and devices.
Photochromic lenses (or transitions), which block UV and blue light indoors/outdoors.

Blue light filtering glasses and lenses may be especially protective among people who have had cataracts surgery, since they are even more susceptible to eye damage caused by too much light exposure.

Shift workers and “night owls” who stay up late some night can also benefit greatly from use of eyewear that blocks blue light if they wish to “reset” their circadian rhythms and fall asleep more easily.

3. Get sunlight exposure during the daytime

Daytime sunlight exposure is important for regulating your circadian rhythm, since it basically sends a signal to your body that helps your brain distinguish daytime versus night time.

If possible, get some sun exposure in the first hour or so of waking up, such as going outside for 10 minutes or more. Try to spend 30 minutes or more outdoors each day to help your eyes get enough light, or be sure to sit close to a window so you at least see some light coming through.

Research suggests that sunlight exposure is also important for proper development of children’s eyes and vision. Too little exposure is believed to potentially contribute to myopia/nearsightedness, so having your children spend time outside each day is encouraged.

4. Consider changing your light bulbs

While LED and fluorescent lights give off more blue light than light bulbs in the past did, there are now some coatings that can be added to the inside of these bulbs can be so they produce a warmer, less blue light. Red, warm light has less of an impact on circadian rhythms and melatonin suppression.

Incandescent lights also produce some blue light, although less than most fluorescent light bulbs. You might not want to use warmer lights in your entire home, but consider putting them in your bed room or anywhere else you spend time before going to sleep.

Other ways to limit blue light exposure include:

Make sure you support your eyes overall, including wearing glasses with the proper prescription if needed.
Keep your eyes moist.
Practice the 20/20/20 strategy, which means stopping every 20 minutes to focus on objects that are 20 feet away for 20 seconds before going to back to viewing your blue light screen.

Final Thoughts

There are both benefits and dangers associated with blue light. Exposure during the day can lead to improved attention, reaction times and moods, but exposure at night can disrupt sleep.
Sources of this type of light include the sun, fluorescent and LED bulbs, and display screens of computers, electronic notebooks, smartphones and other digital devices.
Special blue light filtering glasses can be helpful for decreasing exposure from computers and other digital devices, especially at night. It’s also recommended that you avoid using electronics at least two hours before bedtime and get sunlight exposure during the day.