Lighting Research Center

Advancing the effective use of light for society and the environment

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Light & Health

Light at Night Outdoor Light

There is a growing interest in the role that light plays on human health, particularly nighttime exposure to short-wavelength (blue) light. Exposure to short-wavelength light at night has been shown to suppress melatonin production, thereby disrupting the internal body clock, which can affect sleep and overall wellbeing. However, it has been postulated that the disruption of the internal body clock by reducing nocturnal melatonin might also increase the incidence of disease. Although a logical link may exist between light at night and diseases, it is important to point out that an empirical, scientific link between light at night of a given amount and spectral composition, and an increased risk of disease in humans has not yet been made.

Featured Article:
Lunn RM, Blask DE, Coogan AN, Figueiro MG, et al. 2017. Health consequences of electric lighting practices in the modern world: A report on the National Toxicology Program's workshop on shift work at night, artificial light at night, and circadian disruption.
Science of The Total Environment.

Self-Luminous Devices and Melatonin Suppression

In 2012, the Lighting Research Center (LRC) published a study showing that 2-hour exposure to light from self-luminous devices can suppress melatonin by about 23%. Stimulating the human circadian system to this level may delay sleep in those using the devices prior to bedtime.

LRC conducted a follow-up study published in 2015, showing that adolescents are more sensitive than adults to light from self-luminous devices. Results from the 2015 study show that 1-hour exposure to light from self-luminous devices suppressed melatonin by approximately 23% and 2-hour exposure suppressed melatonin by approximately 38% in adolescents.

Research project summaries are linked below in PDF format.

Self-luminous Devices and Melatonin Suppression in Adolescents pdf logo

Impact of Self-Luminous Tablet Displays on Evening Melatonin Levels pdf logo

Measurement of Light at Night

Several years ago, the LRC anticipated much of the current discussion on light at night as it might affect human health, specifically as a possible carcinogen. Claims of a link between light and cancer (or any other disease) should be substantiated by actual measurements of the light-dark pattern experienced by people. Understanding what the effects of light on human health might be (and accurately measuring them) has been the thrust of the LRC's research in this area. A select list of related publications is below.

Satellite Photometry Is Not a Good Predictor of Actual Light Exposure pdf logo

Media Coverage

LRC research on the effects of light at night has been a popular topic in various media reports. A select sampling is below. For more featured media, visit our Newsroom Media Page.

Sorry, Bedtime Readers: iPads Keep You Awake Even With Night Shift On
Fast Company - February 12, 2018
Exclusive with LRC Director Dr. Mariana Figueiro! New research shows that the "warm" screen color of Apple's Night Shift has a negligible impact on melatonin, although there could be a psychological effect, i.e., warm tones are cited as being more relaxing.

Is Blue Light Bad For Your Health?
WebMD Health News - June 19, 2017
Mariana Figueiro, PhD, light and health program director at the Lighting Research Center in Troy, NY, stresses that in addition to minimizing bright blue-hued light—especially from gadgets held close to the eyes—at night, we should try to maximize the amount of bright light we get during the day. “It not only makes you more awake and alert by day; research suggests it may also make you less sensitive to the negative health consequences of light at night,” she says.

Light at night may disrupt sleep and health
USA TODAY - January 22, 2017
These are among the darkest days of the year — or they would be, if we lived like our ancestors, with nothing but the stars and moon to light our way between sunset and sunrise.

Blue LEDs Light Up Your Brain
Scientific American - November 2016
LRC Light & Health Program Director Mariana Figueiro is featured in this article in the November issue of Scientific American exploring the science of why electronic screens keep you awake at night.

How to Harness the Power of Light to Get Better Sleep
Van Winkle's - June 21, 2016
Until we evolve beyond a light-regulated circadian sleep/wake rhythm, we need to accept the relationship between light and sleep — and understand what we can do to help it along. [This article was also published in Lifehacker.]

Why Your Sleep App Won't Solve Your Sleep Problems
Fast Company - June 2016
LRC Light & Health Program Director Mariana Figueiro is featured in this Fast Company article on sleep tracking apps.

Do Apps Aimed at Making Gadgets Less Disruptive to Sleep Work?
The Wall Street Journal - April 4, 2016
As more people head to bed with smartphones or tablets, there’s increasing focus on the ‘blue light’ the devices emit. [Interview with Mariana Figueiro]

Apple’s New Night Mode Doesn’t Mean You Should Take Your Tablet To Bed
FiveThirtyEight - March 30, 2016
Must read article by Katherine Hobson in Nate Silver's FiveThirtyEight offers a closer look at the science of why screen time can disturb your sleep. [Interview with Mariana Figueiro]

Can Apple's new Night Shift setting help you sleep?
CNN Money - March 25, 2016
"The idea is good, but it is not just about color. The intensity matters too, so color needs to be shifted and intensity needs to be dropped," said Mariana Figueiro in this CNN article, which was picked up by more than 100 news outlets across the U.S.

The new Night Shift feature probably won’t help you sleep better
Macworld - March 25, 2016
Mariana Figueiro's research team is "working on an app that would gather information about your light exposure across a day and recommend the best times to get the right light. With remote-controlled, color-variable bulbs from Hue and others, she suggests a future in which this app could change overall lighting to fit your needs...".

Apple's blue light special can help sleep, but not a panacea
San Francisco Chronicle - March 24, 2016
LRC's Mariana Figueiro speaks with the San Francisco Chronicle about the effect of light on sleep. Article later reprinted in the Houston Chronicle.

To sleep, perchance.
The Economist - May 16, 2015
Screens before bedtime harm sleep. The effect is biggest for teenagers.

Babbage: LEDtime
The Economist - May 11, 2015
Mariana Figueiro's latest study on sleep and light from self-luminous devices is featured in this audio piece that was on the homepage of

8 ways to use your gadgets at night and still get a good night's sleep
Fast Company - February 26, 2015
Michael Grothaus interviews Mariana Figueiro for this article on iPads and sleep.

How Smartphones Hurt Sleep
The Atlantic - February 24, 2015
Blue light makes the brain think it's time to wake up, just as you're getting ready for bed.

Screen time can mess with the body's 'clock'
Science News for Students - February 9, 2015
For a good night's sleep, here is some expert advice: Turn off, turn in and drop off. Anyone who does the opposite—say, turning on an iPad or other similar electronic reader in bed—may have a harder time both dropping off to sleep and shaking that groggy feeling the next morning.

Screen time wrong prelude to bedtime, study says
The Boston Globe - December 22, 2014
Mariana Figueiro speaks with Carolyn Johnson about a new study which confirms her 2012 study results that show backlit tablets can suppress melatonin, delaying sleep.

Bright Screens Could Delay Bedtime
Scientific American - December 2012
If you have trouble sleeping, laptop or tablet use at bedtime might be to blame, new research suggests. Mariana Figueiro of the Lighting Research Center and her team showed that two hours of iPad use at maximum brightness was enough to suppress people's normal nighttime release of melatonin.

Really? Using a Computer Before Bed Can Disrupt Sleep
The New York Times - September 2012
In today's gadget-obsessed world, sleep experts often say that for a better night's rest, Americans should click the "off" buttons on their smartphones and tablets before tucking in for the night. Electronic devices stimulate brain activity, they say, disrupting your ability to drift off to sleep.

View a list of publications, journal articles, and conference papers on light and health issues by Lighting Research Center scientists.








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