blue light

The Adverse Effects of Blue Light

Abbie SawyerThe Research, Your Best Life

blue light

Photo by Curtis Potvin on Unsplash.

Screens and Sleep Don’t Mix

A recent study of 1,500 Americans found that 90 percent of adults use an electronic device within 1 hour of bedtime at least a few times per week. And while many factors can contribute to one’s sleep quality, devices may be an important contributor to insomnia because of the short-wavelength-enriched light that is emitted from them. Exposure to light in the evening and the early part of the night, even at low intensity, has several sleep-disrupting effects: it suppresses melatonin delaying the onset of sleep, shifts the circadian clock to a later time making it harder to fall asleep at a regular hour, and increases alertness and arousal (1).

In one interesting study, 12 adults were randomly assigned reading from a light-emitting (LE) eBook for 4 hours before bed or reading from a print book for 4 hours before bed for 5 consecutive evenings. They found that those reading an LE-ebook displayed decreased subjective sleepiness, suppressed melatonin secretion, lengthened sleep latency (increased time to fall asleep), delayed and reduced REM sleep, and impaired morning alertness (1). 

Why does blue light have this effect? 

Human eyes have rods, cones, and intrinsically photosensitive retinal ganglion cells. Rods and cones are mostly responsible for image-forming vision. Intrinsically photosensitive retinal ganglion cells are responsible for regulating circadian rhythm and other biologic functions. Retinal ganglion cells form the beginning of the neural tract that transmits light data from the retina to the part of the brain that regulates circadian rhythm. Retinal ganglion cells respond powerfully to short-wavelength light like the blue-colored light emitted from most devices and LED televisions. This blue light will cause a high rate of fire from the eyes to the brain, which will change hormonal and circadian rhythms (2).  Blue light also has the ability to stimulate other areas of the brain which are responsible for producing norepinephrine, a neurotransmitter that has potent arousal properties (3).

What can I do?

With the knowledge that the blue light emitted from almost all devices and LED TVs is disruptive to the foundational pathways for sleep, it’s important to take steps to remedy this if you’re having trouble sleeping.

First and foremost, do not use your device in bed. At all. In fact, you should avoid using it at least an hour before you plan to go to bed. Do not watch TV in bed either. If your symptoms are severe, avoid TV for at least an hour before you plan to sleep. 

blue blocker glasses

Photo by Claudio Schwarz | @purzlbaum on Unsplash

If you have to use a device for some reason, avoid long exposure.

You could also consider wearing blue-light blocking glasses for about an hour before bed. The lens blocks the blue light from reaching the retina. Blue-light blockers are commonly made with clear lenses today. You could consider purchasing a pair of these and using them in the evening while you’re using your device. Additionally, they’re thought to help reduce eye fatigue (4). 

Many devices come with a night-shift mode. This mode shifts the hue of the screen to a warmer, redder tone. This has been studied to see if it offset the negative effects of the light from a device. Unfortunately, it did not completely prevent this. Melatonin levels were still reduced when using night shift mode (5). Decreasing the brightness of your device may be more effective at reducing melatonin suppression (5).

Next Steps

If  you’re experiencing restless nights, do yourself a favor and reduce your device usage and blue-light exposure leading up to bedtime. This may have a profound effect on your sleep. For other advice on optimizing your sleep, or if you have questions about supplements that could help your sleep, ask one of our clinicians at your next appointment. Sleep is but one key component to living your best life, day and night.


  1. Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):1232-7.
  2. Molecular Vision 2016; 22:61-72.
  3. Blue-Light Therapy following Mild Traumatic Brain Injury: Effects on White Matter Water Diffusion in the Brain. Front. Neurol. 8:616. 
  4. Ide, T., Toda, I., Miki, E., & Tsubota, K. (2015). Effect of Blue Light–Reducing Eye Glasses on Critical Flicker Frequency. Asia-Pacific Journal of Ophthalmology, 4(2), 80–85.
  5. Sleep, Volume 40, Issue suppl_1, 28 April 2017, Pages A290.

(Adapted from The Chiropractic Success Academy)

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