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Nighttime Blue Light Exposure and Cancer Risk

I read an alarming headline posted by a legitimate cancer treatment center. It proclaimed that the blue light from tablets and smartphones causes cancer — and there I was, lying in bed, reading that headline right off my tablet. Naturally, I clicked the link. And just as naturally, I found that the headline was misleading. While I was relieved to see that the tablet itself was unlikely to cause any disease, I was disappointed to realize that even legitimate hospitals and clinics were readily dispensing misinformation just to drum up clicks or stir anxieties. I decided to dig deeper into the truth behind the blue light link to cancer.

What does the data say?

The facts behind this headline were much more complicated than “blue light causes cancer.” The research referenced was a Spanish study designed to examine the correlation between artificial light exposure. Importantly, in spite of the implications of the headline, the study does not establish any causation. And what it does propose in its conclusion is not that the blue light from tablets or artificial streetlights even causes cancer, but rather that it disrupts the body’s circadian rhythms, thus interfering with sleep. The only link with cancer is the proposition that disrupted sleep patterns may contribute to increased cancer risk.

Correlation does not imply causation

One of the more disturbing aspects of how this article had been posted was the fact that the author was a doctor at the treatment center. Although he may not have written the actual headline, the article itself was framed to imply that reading off a screen at night was somehow dangerous. It includes the easy “fix” of simply changing the color hue of the screen to reduce the exposure to blue light since blue-ish light tricks the body into thinking it is daytime. But the oversimplification of the science and the fear — inducing headline itself — are a sign that it is still important to go one step beyond simply vetting sources before we trust what we read online when it comes to the latest information on cancer risks and treatment.

The fact that this story was picked up with similar headlines by sources like CNN and Men’s Health magazine, suggesting that breast and prostate cancer risk is increased through the use of smartphones at night, is disparaging. But there is some reason to be concerned about nighttime blue light exposure. Studies on both animals and humans suggest that exposure to blue light, the same wavelengths that one would experience on a cloudless day, decrease the amount of melatonin production. Not only does this contribute to disrupted sleep, but it also increased the likelihood of depression in test subjects.

The influence of light

Looking at light as a whole-health issue, it is easy to see why we should be conscientious about our exposure. Some scientists recommend actually increasing exposure to bright light during the day when it increases attentiveness. Natural light is preferred, but bright desktop lights can offer a similar, positive effect, keeping the mind alert. Increased light exposure during the day may also help to make it easier to sleep at night. Meanwhile, nighttime sleep disruption from light exposure has also been linked to obesity and diabetes.

Rather than run away from screens out of fear that they cause disease, however, there are some sensible approaches that will mitigate the risk many people currently perceive. If you live in a place where there is a lot of residual light at night, install blackout curtains or wear an eye mask at night and enjoy a more restful sleep in the darkness. Many experts suggest avoiding any screen exposure for at least an hour before going to sleep, some recommending that there are no screens in the bedroom at all. But if you are like me, using an app to decrease the amount of blue light emitted from my devices in the evening hours is beneficial.

Enhance nighttime sleep

While there is no direct causation established between nighttime light exposure and cancer, there is plenty of evidence to suggest that too much disruption of our body’s circadian rhythm and sleep cycles is reason for concern. And dealing with cancer treatment, sleep becomes a major issue for some patients. What cancer patients do not need, however, is additional anxiety generated from sensationalized headlines. Taking the few small steps to enhance nighttime sleep, on the other hand, may well benefit the patient in unexpected ways, with improved mood, more energy, and an overall healthier experience.

Editor’s Note: We are extremely saddened to say that on October 21, 2018, Jeffrey Poehlmann passed away. Jeffrey’s advocacy efforts and writing continue to reach many. He will be deeply missed.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Is Blue Light Bad For Your Health? WebMD. Accessed on September 2018. From
  2. Blue light has a dark side. Havard Health Publishing. Accessed on September 2018. From