March 15, 2017

If you’re Reading this at Night, Stop. {Blue Light Warning}


When I see patients, they often take out their phones to take notes, check their calendars, or even Google something.

And sometimes, once they’ve completed their screen-related task, they continue to play with their device.

It turns out, being connected to a device or screen at all times is just part of today’s culture.

So, mid-conversation, my patients will text someone at home or respond to a work email. And I make no bones about asking for their undivided attention in those moments. Not just because I think we spend too much time on our devices, but because our devices are actually destroying our bodies.

Usually, patients drop the phone back in their purses or pockets immediately, like it’s no big deal. But, I was surprised recently when a patient refused to put hers down. She told me she was looking for something she absolutely had to show me. I waited patiently until she finally found what she was looking for. And what she showed me…was me!

She’d seen an interview I did on YouTube entitled, “Blue Light is Making You Fat.” She had to know if it was really true. She said she used her phone all day long and she’d just be beside herself if the statement were true. So, I plainly told her, “I’m sorry, but it’s true.”

When we look at a computer screen, a phone, or a tablet, our death clocks speed up. So, it’s best we arm ourselves with some information. In fact, if it’s dark outside right now, anyone reading this page should bookmark it and walk away. Come back and read it when it’s light out.

Here’s why:

This screen—whether it’s on a phone, a tablet, or a computer—is emitting a certain kind of light known as blue spectrum light.

How does blue spectrum light affect us?

Well, special receptors in our eyes use blue spectrum light as a signal to regulate internal processes in our bodies, including:

>> Sleep
>> Wakefulness
>> Immunity
>> Blood sugar

The trouble is, though technology provides us with ease and convenience, screens like this one emit large doses of blue light. Not only that, they do so at all the wrong times. Until recently, the sun was our only source of blue light. So, for most of our human existence, we only saw blue spectrum light during the day.

That’s why our bodies evolved to use blue light as a guide for our internal health clock—also known as our circadian rhythm.

“Health clock” hormones like melatonin are controlled by the body’s exposure to blue light. This rhythm determines when our bodies rest, repair themselves, crave food, and perform a number of other vital activities. I’m not exaggerating in the least when I say our lives depend on the careful timing of all these processes.

And historically, sunlight was a dependable way to set the timer. But unfortunately, this is no longer the case.

In the 21st century, it’s “daylight” all the time.

A little over a decade ago, social media and internet videos began to take off. Touch-screen smartphones exploded in popularity. Touch-pad tablets and Kindles hit the market. And more people than ever before gained access to laptops and computers.

In fact, at this very moment, over 3.56 billion people across the world (including you) are looking at one of these devices.

And, after these folks close their devices, they probably use the flat-screen television in their living rooms, or maybe that touch-screen navigation system in their cars. Perhaps they even go to the gym, where they can hop on that fancy elliptical with the digital monitor attached to it.

And now, the bad news: Light-emitting diodes (LEDs)—which illuminate the screens on all these devices—hit our eyes with a concentrated blast of blue light. In other words, we look straight into blue light sources at all hours of the day and night—including right now.

Our brains are bombarded by unprecedented amounts of blue light at unnatural hours. And with all these blue light signals, our bodies can no longer regulate our internal health clocks properly.

Consequences of all this blue light exposure?

Well, for starters, here’s a little preview:

>> Weight gain
>> Depression
>> Heart problems
>> Metabolic problems
>> Mental problems
>> Constant fatigue
>> Declining health

But first, “How does blue light exposure compromise our health?”

It all starts when our deep sleep gets disrupted.

On more than one occasion, Ivy League researchers have shown blue light exposure suppresses melatonin, making it harder to sleep. (1,2) But recent research shows, even if we do manage to get to sleep, our sleep won’t be “deep” enough.

It turns out, NREM slow-wave sleep—or “deep sleep”—is how our bodies repair the vital organs and systems that keep us alive and healthy. These include the heart, lungs, brain, muscles, digestive tract, and immune system—in other words, all the things we spend our waking hours tearing up through heavy use.

And studies everywhere are now showing that nighttime blue light exposure disrupts our deep sleep patterns. One of these studies was recently conducted at the prestigious University of Basel in Europe.

In this study, 30 healthy adults were exposed to blue light for two hours before bed each night over the course of three months. Scientists discovered that, after the blue light exposure, patients’ deep sleep patterns were bizarrely rearranged. (3)

Shortly after the European sleep study was published, Harvard Medical School conducted their own sleep study right here in the United States. In the Harvard study, doctors monitored the sleep of two separate groups of healthy adults for five consecutive nights. One group read a blue-light-emitting Kindle before bed each night. The other group read a printed book instead.

And what was the result?

The group who read the blue-light-emitting Kindle quickly started experiencing problems that might sound familiar:

>> They took longer to get to sleep.
>> They slept poorly.
>> They were significantly more tired the next morning. (4)

After the fifth night, the doctors running the study tried switching things up. They had the two groups trade reading methods and do another five-night’s sleep cycle. The results were consistent: Whoever used the Kindle experienced sleep problems. (5)

Bottom line: If we expose ourselves to regular and extended sessions of blue light at night, we will stop resting and recovering properly.

Blue light at night is altering our sleep patterns and damaging multiple systems in our bodies.

And once this change occurs, some nasty things start happening. Here are the top five consequences of exposing ourselves to artificial blue light at night:

1. We lose our mental sharpness.

Without adequate deep sleep, our mental and physical abilities deteriorate. Of course, this is common knowledge. But what most people don’t usually realize is how fast it happens.

For instance, those exposed to blue light in the Harvard sleep study were noticeably more exhausted and “spaced out” within just a few days, even though they were still sleeping seven to eight hours per night. (6) Long-term, these effects get worse—a lot worse.

And the really sinister part is, as we get accustomed to being in this state, we stop noticing we’re only running on 50 percent power! And even more alarming…

While we’re having a hard enough time just thinking and functioning, we’re having an even harder time not eating.

And this leads us to the second thing that happens:

2. Our appetite skyrockets, and we gain weight.

See, doctors now know that poor sleep increases ghrelin, the “hungry” hormone, and decreases leptin, the “full” hormone. In fact, Stanford University scientists were warning the medical community about this as early as 2004. (7)

When blue light disrupts our sleep, our ghrelin and leptin go haywire—and we start eating like crazy. In other words, poor sleep makes us feel hungry all the time.

And while we’re busy eating all that extra food, our bodies are busy storing most of it as fat. This was proven in a landmark sleep and obesity study carried out on hundreds of adults over six years in Quebec. When study participants didn’t sleep properly, their metabolism came to a screeching halt.

And this “eat more, store more” cycle does more than just make the fat pile up on our bodies in record time. By slowing our metabolism, the fat becomes nearly impossible to lose.

And, to add insult to injury, weight we gain makes our sleep problems even worse.

Johns Hopkins researchers revealed this in a 2012 study, where they had 77 overweight people slim down to see if they slept better. Many different weight loss methods were used, but the result was always the same:

The more body fat people lost, the better they slept.

And this eye-opening discovery revealed a disastrous loop our evening blue light exposure places us in:

Nighttime blue light exposure ruins our sleep.
Poor sleep forces our bodies to crave more food and store more fat.
Getting fat gives us even more sleep problems.
More sleep problems makes us even fatter…and so on.

By continuing to look at blue light at night, we’re accelerating this vicious, health-destroying cycle.

And as a cardiologist and heart surgeon, I can tell you right now—the long-term consequences of this aren’t pretty. The more weight a person gains, the less real rest a person gets.

3. As blue light disturbs sleep patterns, our blood pressure increases.

The blue light-induced sleep problems we have—especially inadequate deep sleep—wears down the organs and systems.

One of the worst-affected is the heart. Without adequate deep sleep, the heart can’t repair itself properly. It turns out, deep sleep is how the heart recovers from the previous day’s activity. When we start losing this vital section of our sleep cycle, our hearts start wearing down rapidly.

This was demonstrated in a groundbreaking study by doctors at UC San Diego and Harvard Medical School. In this study, 784 men were monitored for both sleep problems and heart problems over the span of 3.5 years.

At the end of the study, the doctors discovered that deep sleep loss increased the chances of hypertension by 80 percent in just a few years. (8)

In other words, when blue light sabotages deep sleep, blood pressure cranks up and starts damaging the heart. And it’s not just the heart that gets damaged. When we get such poor sleep…

4. Our risk of diabetes increases dramatically.

While adequate sleep is decreasing in the U.S., diabetes is rapidly increasing.

In fact, according to a recent report from the CDC, diabetes is at an all-time high—virtually doubling since 1997. (Kind of interesting, since 1997 was around the time the internet first started getting really popular.)

The truth is, poor sleep and diabetes have been linked together in studies conducted at prestigious clinics all over the world. (9,10) And it didn’t take long for University of Chicago Medical School doctors to tie this directly to deep sleep. Deep sleep disruption messes up the body’s ability to regulate blood sugar. (11)

And this chain of events doesn’t stop at our physical and mental well-being either. In addition to everything I’ve already mentioned, our emotions can go haywire, too, and the potential for psychological decline gets very steep, very quickly. That’s because as blue light wrecks our sleep patterns…

5. We plunge head first into depression.

The concept of sleep affecting our moods is nothing new. However, medical researchers are now discovering just how powerful and dangerous the connection is.

A massive sleep-depression study was recently conducted on 1,788 adult twins at the University of Washington Sleep Center. Their findings painted a clear picture:

Poor sleep nearly doubled the participants’ risk for developing depression. (12)

And new studies like this are coming out every year. The body of evidence is growing so rapidly, Dr. Lawrence J. Epstein at Harvard Medical School had this to say:

“People who have problems with sleep are at an increased risk for developing emotional disorders—anxiety and depression. There’s a very strong link.” 

So, to put it all together:

Let’s bring it all back to blue-light-emitting screens. Consider the following facts:

1. Daily internet “screen time” exploded between 2008 and 2012.
2. Prescriptions for heart, diabetes, and depression medications ramped up during the same period. (13)

Chronic diseases are increasing alongside the use of blue light devices. And as a cardiologist, I’ve had to write quite a few of those heart medicine prescriptions myself. I do not want to have to write too many more if we can help it!

So, what can we do about it?

Alright, I know blue-light-emitting devices are unavoidable. And besides, our bodies are already designed to get blue light during the day. The main issue here is blue light at night. So, here are a few precautions to minimize nighttime blue light exposure:

1. Read a real book at night using regular light.

In other words, don’t use an Kindle or tablet. Save those for the daytime. And don’t use a fluorescent book light, as those put off a ton of blue light.

2. When using a computer at night, try blue-light blocking lenses.

Studies show blocking blue light with amber lenses improves both sleep and mood. So, for those who must be on their cell phones, computers, or tablets late at night, these lenses are a good option.

And there are tons of brands—Uvex Skyper, Gamma Ray, Gunnar—the list goes on. Find the right pair, and sleep easier! (I know I do.)

3. Limit looking at screens for long periods of time.

This is crucial! How often does a person reach for his cell phone—while reading this article? How many hours a day does a person look at her computer or tablet?

Looking at screens has become a widespread addiction. It’s a nervous habit we have when we don’t know what to do with ourselves. (I know, I’m guilty of this too.) Not to mention, it’s a major means of communication.

But, I have a suggestion:

When we feel the impulse to reach for our devices, we should go for a walk. Or have a real, in-person, face-to-face conversation with someone. Half the time we’re buried in a phone screen, we’re ignoring someone right in front of us (who’s also probably buried in a phone screen).

Put the phone down. Ask them to do the same. Ask them a question that throws them off guard. Get to know them better. Or call someone instead of texting—it is a phone after all!

I promise, doing this feels better than shooting off another text. Plus, it relieves us of looking at the blue light. Remember, we evolved to communicate with our voices. That’s where our real humanity is!

If we all spent less time on our phones, laptops, and tablets, we’d all be much healthier and happier.

Life is out there in the world, not on this screen. So, how about sharing this article with whomever—a friend or anyone who might need to see it. Then, leave a comment telling me what you’re about to go out in the world and do…and then close this device and go do it!



1. Gooley JJ, Chamberlain K, Smith KA, et al. Exposure to Room Light before Bedtime Suppresses Melatonin Onset and Shortens Melatonin Duration in Humans. J Clin Endocrinol Metab. Mar 2011; 96 (3): E463–E472. DOI: 10.1210/jc.2010-2098.
2. Lockley SW, Brainard GC, Czeisler CA. High sensitivity of the human circadian melatonin rhythm to resetting by short wavelength light. J Clin Endocrinol Metab. Sep 2003; 88 (9):4502-5. DOI: 10.1210/jc.2003-030570.
3. Chellappa SL, Steiner R, Oelhafen P, Lang D, Götz T, Krebs J, Cajochen C. Acute exposure to evening blue-enriched light impacts on human sleep. J Sleep Res. Oct 2013; 22 (5): 573-80. DOI: 10.1111/jsr.12050.
4. Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci U S A. Jan 27, 2015; 112 (4): 1232-7. DOI: 10.1073/pnas.1418490112.
5. Id. at 1232-7.
6. Id. at 1232-7.
7. Taheri S, Lin L, Austin D, Young T, Mignot E. Short sleep duration is associated with reduced leptin, elevated ghrelin, and increased body mass index. PLoS Med. Dec 2004; 1 (3): e62. DOI: 10.1371/journal.pmed.0010062.
8. Fung MM, Peters K, Redline S, Ziegler MG, Ancoli-Israel S, Barrett-Connor E, Stone KL; Osteoporotic Fractures in Men Research Group. Decreased slow wave sleep increases risk of developing hypertension in elderly men. Hypertension. Oct 2011; 58 (4): 596-603. DOI: 10.1161/HYPERTENSIONAHA.111.174409.
9. Larcher S, Benhamou PY, Pépin JL, Borel AL. Sleep habits and diabetes. Diabetes Metab. Sep 2015; 41 (4): 263-71. DOI: 10.1016/j.diabet.2014.12.004.
10. Knutson KL, Van Cauter E. Associations between sleep loss and increased risk of obesity and diabetes. Ann N Y Acad Sci. 2008; 1129: 287-304. DOI: 10.1196/annals.1417.033.
11. Tasali E, Leproult R, Ehrmann DA, Van Cauter E. Slow-wave sleep and the risk of type 2 diabetes in humans. Proc Natl Acad Sci U S A. Jan 22, 2008; 105 (3): 1044-9. DOI: 10.1073/pnas.0706446105.
12. Watson NF, Harden KP, Buchwald D, Vitiello MV, Pack AI, Strachan E, Goldberg J. Sleep duration and depressive symptoms: a gene-environment interaction. Sleep. Feb 1, 2014; 37 (2): 351-8. DOI: 10.5665/sleep.3412.
13. Kantor ED, Rehm CD, Haas JS, Chan AT, Giovannucci EL. Trends in Prescription Drug Use Among Adults in the United States From 1999-2012. JAMA. Nov 3, 2015; 314 (17): 1818-31. DOI: 10.1001/jama.2015.13766.


Author: Dr. Steven Gundry

Image: Jay Wennington/Unsplash

Editor: Catherine Monkman

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