The Truth About Blue Light, Sleep and Health: Light from LED Screens (TV's Computers, IPads, Tablets and Cell Phones)

Does Blue Light from LED Screens (TV's Computers, IPads, Tablets and Cell Phones) Disrupt Your Sleep or Harm Your Eyes?

Blue light is emitted by LED screens such as those used in cellphones, ipads, computer monitors, TVs, kid's video games etc. These LED screens have only been in wide use for a few years, so the effects of their use is just now becoming understood.

Here is what is emerging:

  • Wavelength Chart of LightBlue light from these devices may disrupt sleep patters
  • The UV light from these devices may be linked to increased macular degeneration and other health problems.

OK, those are the headlines. But how real is this? Is this yet another example of the media pointlessly scaring people and opticians and eyeglass seller trying to profit by selling blue light filters?

Blue light spectrumWhat is Blue Light?

Visible light, the light humans are able to see, is measured in the the range from 380 nanometers (nm) to 780 nm. Ultraviolet light (UV) starts just past the shorter end of the visible spectrum, meaning it is not visible to the human eye. Blue light is the range of visible light, which we see as the color blue, just before the ultraviolet light range begins. The visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere. This causes the sky to appear blue. blue spectrum.

Ultraviolet (UV) Light

Related to blue light is Ultraviolate light. We include this not to confuse it with blue light, but to because it is closely related, as it is in the range of light radiation just past visible blue light. It is divided into 3 ranges: UVA, UVB and UVC.

  • UVA- 315 nm to 380 nm. It causes sun tanning, and while that causes aging of the skin and can contribute to skin cancers, UVA is the least damaging of the UV light ranges.
  • UVB - 280 nm to 315 nm. UVB causes sunburns, destruction of vitamin A, skin wrinkling, cataracts, melanomas and other skin disease. Exposure to UVB is cumulative to both the body and the eyes.
  • UVC - 100 nm to 280 nm. UVC is the most dangerous of the UV light. Most UVC light does not reach the earth's surface as it is absorbed by the ozone layer in the upper atmosphere.

Blue Light and Sleep

Our bodies have their own biological clock, with it's own sleep/wake cycle, which is called the circadian rhythm. While each person has a slightly different circadian rhythm, the average length is 24 hours 15 minutes. Which also explains why, we go through periods when we tend to stay up later and wake up later - unless we reset the clock by exposure to sun light. And night owls tend to have circadian rhythms that are slightly longer (maybe 25.5 hours) that early birds who may be 23.5 hours. According to Harvard Medical School, research shows that disrupted sleep patterns may contribute to the causation of cancer, diabetes, heart disease, and obesity. Melatonin, a hormone that influences circadian rhythms, rises and falls throughout the day, and its levels are also related to exposure to light.

In Harvard's article, Stephen Lockley, a Harvard sleep researcher is quoted as saying even dim light, as low as 8 lux (click here for "what is Lux") can interfere with a person's circadian rhythm and melatonin secretion. For comparison, nightlights are usually around 4 lux.

Blue wavelengths of visible light help to reset our biological clock, which is why travel experts advise travelers to go outside in the morning after crossing many time zones. This helps to improve alertness, attention, reaction times, and mood. But at night, exposure to blue light can have the work against our sleep -wake cycle, making us feel more awake, when we need to be falling asleep.

Blue Light and Health

Many studies have shown that people who work night shifts or have exposure to light at night, have higher rates of several types of cancer (breast, prostate), diabetes, heart disease, and obesity. The theory is that since exposure to light suppresses the secretion of melatonin, a hormone that influences circadian rhythms, and there's some experimental evidence (it's very preliminary) that lower melatonin levels might explain the association with cancer.

Blue Light and Macular Degeneration (AMD)

According to the American Macular Degeneration Foundation (AMDF) Ultra-violet and Blue Light Ultra-violet light (invisible light below 286nm to 400nm) is "generally understood to be harmful to the eye, possibly leading to cataracts and other eye diseases such as age-related macular degeneration (AMD)". The AMDF says recent studies suggest that the blue end of the light spectrum may also contribute to retinal damage and possibly lead to AMD. The retina can be harmed by high-energy visible radiation of blue/violet light that penetrates the macular pigment found in the eye. According to a study by The Schepens Eye Institute, a low density of macular pigment may represent a risk factor for AMD by permitting greater blue light damage.

Notice that they said "high-energy visible radiation of blue/violet light". Other authorities suggest that the risks may be exaggerated, since the personal electric devices emit very low levels, not high levels!

Positions saying that Blue Light from device screens is dangerous

  • Why Is Blue Light before Bedtime Bad for Sleep? Two neuroscientists discuss how blue light negatively affects health and sleep patterns, By Jessica Schmerler on September 1, 2015 (Scientific American): "Scientific American MIND consulted with Thomas Jefferson University neuroscientist George Brainard, who was among the first researchers to investigate how different wavelengths of light affect the release of melatonin, and Harvard University neuroscientist Anne-Marie Chang, who recently discovered that the effects of light-emitting devices on circadian systems extend beyond evening and into the following morning."
  • Essilor and the Paris Vision Institute study: The blue-violet light that was discovered as part of this study is a 40 nm band of visible light that causes the maximum retinal cell death. Over time, our eyes are exposed to various sources that emit this blue-violet light (e.g., the sun, LED lighting, CFLs). Combine that with the use of tablets, TVs, computer screens and smart phones, and there's no doubt our exposure to blue-violet light is on the increase. This cumulative and constant exposure to the blue-violet light is going to accumulate over time and has the potential to cause damage to the retinal cells, which is going to slowly lead to retinal cell death and can in turn lead to AMD.

Positions saying that the risk is minimal or substantially overstated

  • Despite concerns that staring at devices putting out high amounts of the blue light wavelength could damage human retinas, a recent study finds that most devices put out less of that light than the blue sky on a clear day. "Even under extreme long-term viewing conditions, none of the low energy light bulbs, computers, tablets and mobile phones we assessed suggested cause for concern for public health," said lead author John O'Hagan, head of the Laser and Optical Radiation Dosimetry Group of Public Health England in Chilton, U.K.
  • OLED-Info,, "A senior VP at LGD recently declared in the IMID Display Business Forum in Korea that according to measurements done by the company, LCD screens emit 3.1 times more blue light than OLED screens. The measurements were done 120 cm away from TVs, 60 mm from monitors and 30 cm from smartphones (TVs are larger and emit more blue light than other types of screens)."


  1. Exposure to sources of blue light radiation at higher intensities and longer durations at night disrupts sleep patterns
  2. Disrupted sleep patterns can lead to many adverse health effects.
  3. Exposure to sources of light radiation, especially UV and the blue end of the visible spectrum, at higher intensities and longer durations at any time may lead to cataracts, macular degeneration and other physical health problems.
  4. Inconclusive is the definition of a dangerous level or duration of blue light exposure

Since there are not yet adequate studies to determine dangerous vs. safe levels of exposure, the best approach is use reasonable and practical methods to reduce exposure. See below.

What Can You Do To Reduce Your Risks?

See the suggestions below. The links open relevant windows on to see examples.

  1. Sit farther away from screens
  2. Avoid using devices 2 to 3 hours before bedtime
  3. Use filters on computer screens - see an assortment of effective filters available through Amazon at right
  4. Usefilters on cell phones and filters on ipads and other tablets
  5. Wear eyeglasses and sunglasses that have blue light filter coatings
  6. Use newer OLED screens (typically on TVs and computer monitors) rather than older LCD screens.
  7. Use red colored nightlights, especially for children.
  8. When choosing light bulbs, look for "warm white" rather than 'Cool white" lights. Warmer means less blue light.
  9. Expose yourself to lots of bright light during the day, such as outside (wearing UV filtering sunglasses) which will boost your ability to sleep at night, as well as your mood and alertness during daylight.


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