Category: Science

Night Time Light Exposure – Not a Bright Idea

We live in a very light polluted world in comparison to that of our very recent ancestors. Estimates now indicate that close to 99% of both Americans and Europeans are exposed to “light pollution.” Not only are we excessively exposed to light in modern times, but the type of light accounting for this exposure is changing rapidly. As we move away from incandescent lights in favor of light emitting diode (LED) technology, we are seeing an ever-increasing exposure to a particular part of the light spectrum – blue light, that has been associated with some worrisome effects in terms of human health.

New research shows that blue light exposure significantly reduces the amount of melatonin secreted by the brain’s pineal gland. This has obvious detrimental effects on both the duration as well as quality of sleep. Reduced quality of sleep has been associated with a number of issues including obesity, diabetes, and even Alzheimer’s disease.

In an interesting study, Spanish researchers evaluated 623 men with a diagnosis of prostate cancer and compared them to 879 male controls. Exposure to light from indoor sources at night was computed using a questionnaire, while outside exposure was calculated using data from the International Space Station. The latter data specifically allowed for the collection of information related to blue light exposure.

The study was carried out as it is known that light exposure may significantly alter hormone activity, and prostate cancer is a hormone related event. Further, previous research has demonstrated that night shift workers are known to have an increased of prostate cancer.

The researchers found that comparing those with the highest exposure to blue light to those with the lowest, the risk of prostate cancer was more than doubled. The risk was almost tripled in men who had high levels of light in their rooms when they slept in comparison to men who slept in “total darkness.”

So this is yet another argument in favor of considering the doctrine of the “paleo” movement. That is, there are health benefits associated with trying to emulate the environments of our ancestors. In this case, keeping in mind that when the sun went down, our ancestors were pretty much in the dark. And this history is recapitulated in our genetic code.

The important points here are that first, we should dramatically reduce our exposure to light as we approach and engage sleep. And the second, but nonetheless equally important point is that blue light, the kind emitted by our phones, computer screens and tablets, seems to be particularly disruptive of hormone activity and, according to this research, may well enhance the risk of prostate cancer.

For more information on sleeping soundly, please watch this video.

  • Lynn Dell

    I bought some special glasses Dr. Amy Myers recommended, but am not consistent wearing them. After going on a couple of extended water fasts this year (5 days or more), I noted it is now much easier for me to get to sleep, and usually to stay asleep for a refreshing night of sleep. This is after 3 days of fasting and post fast. Days 1 to 2 1/2 I often struggle with pain from old injuries and coffee withdrawal, and it is so great to get past that. I know nothing of fasting and sleep studies; just saying I clearly noted falling and staying asleep much easier for a considerable time post extended fast. Thanks, Dr, Perlmutter.

    • sugarboo

      Maybe you are sleeping better because you are not drinking your coffee, which has caffeine, and is stimulating beyond the morning when you drink it.

      • Lynn Dell

        Maybe. I’ve cut back on coffee. I notice even when I drink it I’m still sleeping better. But perhaps I’ve cut back to a sweet spot so the level of caffeine is ok for me.

  • Nanook

    I switched to some blue light blocking (Swanwick), reader type glasses. When I take them off, I cannot believe how bright the blue light is on my iPad now! I get somewhere between 10-20% more sleep just using the blue blocking glasses before bedtime. The blue light is very intense off these devices, you don’t realize how much until you switch to a blue – blocking lense.

  • jeanne brick

    I recently learned that in the Sierra upgrade on apple products there is a choice to have the blue light from the screen automatically diminished from sundown to sunrise. The screen has a rosy glow instead of the blue light. I had been planning to purchase a blue light filter to apply on the screen before discovering this.

    • David Perlmutter

      Yes, and I use that feature on my iPhone frequently!

  • Yvonne Hedeker

    It would be more help to your followers to differentiate between blue-violet under 455nm and blue-turquoise over 455nm. Not all blue light is created equal. The shorter wavelength used in technology can be potentially harmful with overexposure a d lenses are now made to block blue-violet. The longer wavelengths are good and are used in healing. The media is jumping on this topic without fully understanding the difference.

  • Andy

    Please proofread.

  • Cyrus Earl Rojo

    Thank you Dr. David. I just learned about melatonin last June as my Mother was prescribed with melatonin capsule. Her physician explained to us that our body can’t produce melatonin normally when we are exposed to light while sleeping. I just realized that my grandparents we’re still healthy maybe with the help not exposing themselves with light at night time.

  • Lynne Gray

    can install f.lux on computer too which cuts down blue light. It’s great!!

    • David Perlmutter

      Great suggestion Lynne!


    Dear Dr. Perlmutter sorry but I have a question for another subject, can you please explain me what is exactly
    I am living in Spain and following you already for 4 years and we are buying al the complemets as probiotic , resveratro and so on from the USA but now the Spanish customs don’t accept anymore goods from the USA so we are searching for another way.
    Hendrikus Zomer

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