Translate this page to any language by choosing a language in the box below.
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
Here is what is emerging:
Blue 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?
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
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
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
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)."
- Exposure to sources of blue light radiation at higher intensities
and longer durations at night disrupts sleep patterns
- Disrupted sleep patterns can lead to many adverse health effects.
- 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.
- 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
Amazon.com to see examples.
- Sit farther away from screens
- Avoid using devices 2 to 3 hours before bedtime
- Use filters on computer screens -
see an assortment of effective filters available through Amazon at right
- Usefilters on cell phones and
filters on ipads and
- Wear eyeglasses and sunglasses that have blue light filter coatings
- Use newer OLED screens (typically on TVs and computer monitors)
rather than older LCD screens.
- Use red colored nightlights, especially for children.
- When choosing light bulbs, look for "warm white" rather than 'Cool
white" lights. Warmer means less blue light.
- 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.
Harvard Medical School Harvard Health Letter - "Blue light has a dark side" "Light at night is bad for your health, and
exposure to blue light emitted by electronics and energy-efficient light
bulbs may be especially so."
NASA - "What Wavelength Goes With a Color?"
Endocrinol Lett. 2011;32(2):158-63."The impact of light from computer
monitors on melatonin levels in college students.", Figueiro MG1, Wood B, Plitnick B, Rea MS. RESULTS: Melatonin
concentrations after exposure to the blue-light goggle experimental
condition were significantly reduced compared to the dark control and to
the computer monitor only conditions. Although not statistically
significant, the mean melatonin concentration after exposure to the
computer monitor only was reduced slightly relative to the dark control
condition. CONCLUSIONS: Additional empirical data should be collected to
test the effectiveness of different, brighter and larger screens on
- "Blue light from screens, bulbs may be too weak to damage eyes",
BY MADELINE KENNEDY Fri Jan 29, 2016 12:45pm EST Related:
Review of Optometry - "The Lowdown on Blue Light: Good vs. Bad, and Its Connection to AMD", Release Date: February 2014
The Royal Society Publishing - "Electric light, particularly at night, disrupts human circadian rhythmicity: is that a problem?",
Richard G. Stevens, Yong Zhu. Published 16 March 2015.DOI: