Does a Study Change What We Know About Blue Light?

Analysis by Dr. Joseph Mercola Fact Checked

blue light sleep disturbances

Story at-a-glance -

  • Evidence from a small study found that blue light helped mice sleep better — but before we change the way we think about blue light’s effect on humans, studies need to be done on humans, at least one researcher says
  • Blue light is linked to many well-documented health risks, including sleep problems
  • The use of blue light-emitting smartphones, computers, tablets and e-readers before bedtime is linked to sleep disturbances
  • Whether future research shows blue light disturbs sleep or not, it’s best to avoid it and let your natural circadian rhythm work

Artificial light is a relatively new development in terms of human evolution. Before we could create "day" out of night, humans woke up with the sun and went to bed when the sun set. Some studies suggest that before artificial light, humans experienced biphasic sleep; they slept in two shifts during the night, using their sleep break for prayer, reflection or reading by candlelight.1

Artificial light permanently changed the way we live, in many ways for the better. But there has been a second change since the invention of artificial light that might be more consequential: the proliferation of electronic devices that create "blue light." To that end, 96 percent of Americans now own cellphones, mostly smartphones, and 75% own desktop or laptop computers. About 50% own tablets and e-readers.2

Blue light rays are the shortest wavelengths of light and constitute one-third of all the sunlight we see.3 But smartphones, computers, tablets, e-readers, TVs and LED (light-emitting diode) and CFL (compact fluorescent lamp) lighting also emit blue light and have significantly added to the amount of blue light we now receive.4

There are many well-documented risks associated with exposure to blue light from these electronic devices, one being impaired sleep. As such, we’re advised to tone down or completely avoid blue light at night. Interestingly, researchers at Manchester University discovered that blue light associated with twilight actually helped mice sleep better — opposite of current thinking on blue light’s effect on sleep.5

It was a single study using small groups of mice (seven to eight mice in an average group) but if the same proves true for humans, it could change everything we know about using blue light at night, lead researcher Tim Brown told BBC:6

“During the daytime, the light that reaches us is relatively white or yellow and has a strong effect on the body clock and around twilight, once the Sun sets, the bluer the light becomes," he said. "So if you want to avoid light having a strong effect on your body clock, dim and blue would be the way to go …

"At the moment, often what people are doing is adjusting the colour of lighting or visual displays and making the screens more yellow. Our prediction is that changing the colour is having exactly the wrong effect. It's counteracting any benefit that you might get from also reducing the brightness of the screen."

In other words, blue lights may actually induce sleep, rather than impair it. Moreover, the yellow and orange lights with which many people have sought to replace blue lights, especially at night, may actually be the light waves that disrupt and harm sleep.

But before we run off and change the rule books on the topic, at least one scientist says not so fast. For one thing, mice are nocturnal; they’re naturally active at night, while humans are typically sleeping. Blue light helping mice sleep doesn’t necessarily make it true for humans, says Manuel Spitschan, Ph.D., a research fellow with an interest in visual and nonvisual responses to light in humans.

“This is fascinating work, but we really don’t know yet that the same happens in humans,” Spitschan told BBC. “That’s the difficulty with animal work. It should be possible to do tests with people in the future to find out for sure.”

Study Questions a Well-Accepted Hypothesis

Search for "blue light" on the internet and you will find hundreds of health and medical sites that warn you about the harmful effects of blue light on your sleep. Here is what the National Sleep Foundation says:7

"The reason that blue light is so problematic is that it has a short wavelength that affects levels of melatonin more than any other wavelength does.

Light from fluorescent bulbs and LED lights can produce the same effect. Normally, the pineal gland in the brain begins to release melatonin a couple of hours before bedtime, and melatonin reaches its peak in the middle of the night.

When people read on a blue light-emitting device (like a tablet, rather than from a printed book) in the evening, it takes them longer to fall asleep; plus, they tend to have less REM sleep (when dreams occur) and wake up feeling sleepier— even after eight hours of shuteye."

I have often warned about the effect of blue light on sleep and recommended "blue blocker" glasses to protect your eyes at night. So, if this new research, published in the journal Current Biology,8 is true, it could have far-reaching repercussions on how humans approach the use of blue light at night in the future.

Brown explained the new thinking and the role of melanopsin, a photo pigment expressed in retinal ganglion cells, in light-affected sleep, this way:9

"We show the common view that blue light has the strongest effect on the clock is misguided; in fact, the blue colours that are associated with twilight have a weaker effect than white or yellow light of equivalent brightness.

There is lots of interest in altering the impact of light on the clock by adjusting the brightness signals detected by melanopsin but current approaches usually do this by changing the ratio of short and long wavelength light; this provides a small difference in brightness at the expense of perceptible changes in colour.

… We argue that this is not the best approach, since the changes in colour may oppose any benefits obtained from reducing the brightness signals detected by melanopsin. Our findings suggest that using dim, cooler, lights in the evening and bright warmer lights in the day may be more beneficial."

More Blue Light Questions From the Study

It has been almost an article of faith that the warmer, "yellow" tones of light will not disrupt your sleep, like the blue ones. In fact, over the last few years, many have protested cities' conversion to LED streetlights because of their apparent association with poor sleep, higher cancer rates and glare.10 As many as 10% of U.S. municipalities now use LED streetlights for their longer life, energy savings and quality of light.

On a micro level, many computers and smartphones now contain warm, yellow "night tones," which you can switch on a few hours before bedtime. But according to the Manchester researchers, science may have the light effects backward. They write:11

"We found that changes in phase (activity midpoint) produced by L+S (yellow) stimuli were significantly more rapid than L S+ (blue) for both delay and advance shifts …

… When biased toward S-opsin activation (appearing ‘‘blue’’), these stimuli reliably produce weaker circadian behavioral responses than those favoring L-opsin (‘‘yellow’’) … Contrary to common beliefs, it is yellow rather than blue colors that have the strongest effect on the mammalian circadian system."

This means that if humans truly are affected the same way mice are, yellow night screens could possibly contribute to the very insomnia we are trying to avoid.

According to the study, the type of glow emitted by yellow and orange flames from a fireplace could paradoxically have a stimulating effect rather than inducing sleep. The findings, if validated, would also explain why people often fall asleep in front of the blue light of the television.

There are two reasons for blue light's "bad rap," speculate the Manchester University researchers. First, the effect of the differing wavelengths of yellow and blue light — blue light being much shorter — was confused with, and attributed to, their colors. Second, previous scientists failed to focus on the fact that light becomes very "blue" at twilight so our natural rhythms find it soporific.

But, as the Oxford scientist stressed, we don’t know if this study is applicable to humans or not and, indeed, further research is necessary before we can extrapolate that the effects of blue light on humans have been misinterpreted.

General Sleep Advice Is Still Valid

In the meantime, whether blue light proves to be further implicated in insomnia in humans or not, there are still reasons to disengage from your electronic devices before bedtime — and yellow light is not the answer. Christian Benedict, associate professor at the department of neuroscience at Uppsala University and author of a 2016 study published in the journal Sleep,12 told Consumer Affairs:13

"'It must however be kept in mind that utilizing electronic devices for the sake of checking your work e-mails or social network accounts before snoozing may lead to sleep disturbances as a result of emotional arousal."

Benedict’s study suggests receiving daytime bright light exposure, a practice that I encourage, can help offset sleep disturbances caused by exposure to electronic devices at night. Here are some additional important suggestions for a good night's sleep, regardless of where the blue light controversy ends.

Sleep in complete darkness — Even the tiniest bit of light in the room, such as that from a clock radio LCD screen, can disrupt your internal clock and your production of melatonin and serotonin, thereby interfering with your sleep (and raising your risk of cancer).

Keep the temperature in your bedroom no higher than 70 degrees F — Studies show the optimal room temperature for sleep is between 60 and 68 degrees F. Keeping your room cooler or hotter can lead to restless sleep. When you sleep, your body's internal temperature drops to its lowest level, generally about four hours after you fall asleep.

Eliminate electric and electromagnetic fields (EMFs) in your bedroom — These can disrupt your pineal gland's production of melatonin and serotonin, and are a significant contributor to mitochondrial damage and dysfunction, which is at the heart of virtually all chronic disease.

Move alarm clocks and other electrical devices away from your bed, and avoid using loud alarm clocks — If you need to use these devices, keep them as far away from your bed as possible, preferably at least 3 feet. Keep your cellphone as far away from your bedroom as possible if you feel it must be on, or put it in airplane mode. Better yet, if you keep it in your bedroom, shut it down.

Adopt a neutral sleeping position — If you're a side- or stomach sleeper and find yourself frequently tossing and turning at night and/or waking up with aches and pains, your sleeping position may be a primary culprit.

Reserve your bed for sleeping — If you are used to watching TV or doing work in bed, you may find it harder to relax and drift off to sleep, so avoid doing these activities in bed.

Consider separate bedrooms — Studies suggest that, for many people, sharing a bed with a partner can significantly impair sleep, especially if the partner is a restless sleeper or snores. If bedfellows are consistently interfering with your sleep, you may want to consider a separate bedroom. You may also need to banish your pets from the room if their presence impairs your sleep.

Beware of Quick-Fix Sleeping Medications

Regardless of what additional research about blue light might reveal, it’s certainly true that more Americans than ever suffer from poor sleep and insomnia. Most reasons stem from an urban, "workaholic" lifestyle that encourages people to squeeze sleep in between their other busy activities, rather than make restorative sleep a top health priority.

Sadly, drug makers have tried to cash in on Americans' sleep problems by aggressively advertising sleeping pills and other types of sedatives even though they are likely to make the situation worse. For example, in 2013, the Journal of Hospital Medicine reported a strong association between the popular sleeping pill Ambien (zolpidem) and falls.14

More Sleep Medication Dangers

Just as dangerous as falls, "complex sleep behaviors" such as sleepwalking, sleep driving and using a stove while not fully awake, which pose the "risk of serious injury and death," are associated with three popular sleeping pills (eszopiclone, zaleplon and zolpidem), says the FDA.15 Warnings about such behaviors were already on the drug labels, and strengthened, in April of 2019.

Nevertheless, seeing the great profit in sleep medications, drug makers have rolled out a host of particularized sleep disorders: chronic, acute, transient, initial and middle-of-the-night insomnia, early-morning wakening disorder and non-restful sleep disorder — all of which they claim require specific medications.

The irony is that almost all insomnia and poor sleep can be treated with a healthier lifestyle and sleep hygiene. Moreover, when people try to stop taking sleep medications, they often experience rebound effects and their sleep may become worse, not better, from the drugs.

Adding to the problems, drug makers have also discovered the profit in drugs that treat "excessive sleepiness" and more obscure sleep conditions such as non-24-hour sleep-wake disorder, shift work sleep disorder and narcolepsy. These conditions and the drugs that treat them are now aggressively advertised, a strategy that grows awareness of the so-called conditions, as well as the pool of potential patients.

Since most drugs for these conditions stimulate the body, they likely can cause more sleep problems and lead to more drugs. Is it any surprise, then, that sleeping problems are getting worse, not better, in the U.S.?

Needless to say, coffee and cigarettes also make sleep problems worse. Alcohol can help you fall asleep faster, but it makes sleep more fragmented and less restorative. If you want more information on how to achieve better sleep, don't forget to refer to my "33 Secrets to a Good Night's Sleep."

The Take-Home Message on Blue Light

Studies have linked blue light with many serious effects, including:

Macular degeneration16

Shortened lifespan17

Insulin resistance and metabolic disorders

Myopia and eye strain

Mitochondrial dysfunction


So, until actual human studies are done and research on blue light shows similar results to the mouse study, the best thing to do is avoid it and try natural ways to work with your own circadian rhythm, using sleep strategies that we know will work.