Lighting Research Center

Advancing the effective use of light for society and the environment

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Light & Health

Light, Alertness, and PerformanceAlertness

Alertness is associated with high levels of environmental awareness, high levels of wakefulness and low levels of fatigue, and faster mental capacity. Alertness has been shown to be strongly influenced by exposure to light and the timing of the circadian clock: alertness is lower during nighttime hours, when there are high levels of the hormone melatonin and core body temperature levels are low. Melatonin signals sleep to diurnal species, such as humans, but can be suppressed by exposure to light at night. Understanding how light affects alertness can have far-reaching implications, from decreasing sleepiness and increasing productivity in the workplace to helping airline passengers adapt to a new time zone after a long flight.

The LRC has conducted several laboratory studies and field demonstrations to investigate the impact of short- and long-wavelength light on alertness and performance. It has been shown that the circadian system is highly sensitive to short-wavelength blue light, but long-wavelength red light has recently been shown to increase objective measures of alertness at night as well as during the day. Some recent research projects regarding the effects of light on alertness and performance are highlighted below.

General Research

Circadian Lighting for U.S. Navy Submarines pdf logo

Light, not the Alarm Clock, Controls the Times We Sleep pdf logo

Light's Effects on Alertness

Scientists at the LRC are currently investigating the effects of colored light on alertness, as well as the effects of light exposure on alertness throughout the 24-hour day. Summaries of select research projects are linked in PDF format.

 Effects of White Light on Melatonin Suppression pdf logo

  • Light and Health Alliance
  • Lumileds

 Circadian Light and Its Impact on Alertness in Office Workers pdf logo

  • General Services Administration

Red Light Improves Nighttime Alertness and Performance pdf logo

Daytime Light Exposure: Effects on Biomarkers, Measures of Alertness, and Performance pdf logo

The Impact of Red and Blue Lights on Alertness in the Afternoon pdf logo

New Pathway to Alertness pdf logo

Effects of Red and Blue Light on Alertness, Sleepiness, and Mood pdf logo

Light as an Alerting Stimulus for the Circadian System pdf logo

Light, Performance, and Sleepiness

 Red Light Delivered During Sleep to Reduce Sleep Inertia pdf logo

  • Office of Naval Research

Effects of Chronotype, Sleep Schedule and Light/Dark Pattern on Circadian Phase pdf logo

Impact of Sleep Duration and Light Exposure on Sleepiness and Performance pdf logo

Daylight with Blue or Red Lights Affect Performance and Sleepiness at Night pdf logo

Media Coverage

LRC research on light, alertness, and performance has been been featured in various media reports. A select sampling is below. For more featured media, visit our Newsroom Media Page.

New studies show cycles of blue and red light promote circadian entrainment
LEDs Magazine - December 2019
LRC collaboration with GSA finds morning blue light and afternoon red light promote entrainment and increase alertness in office workers.

Shine a Healing Light: Circadian-Based Lighting in Hospitals
Medscape Medical News - February 28, 2018
"Giving hospital patients a robust light/dark lighting pattern is the most logical thing to do to promote synchronization of the body's biological clock, and we're seeing many health benefits." --Interview with Dr. Mariana Figueiro

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.

Daily Wisdom: Morning sun can get you on a better sleep schedule
Furthermore - June 14, 2017
Interview with Dr. Mariana Figueiro, Professor and Light and Health Program Director at the Lighting Research Center. "Seek light during the day from any source, electric or daylight, especially in the morning," she advises.

To improve your productivity, paint your office this color
MarketWatch - April 1, 2017
Color — specifically, colored lighting — can affect productivity, according to an extensive body of research by Mariana Figueiro, a professor at the Lighting Research Center, Rensselaer Polytechnic Institute, a private research university in Troy, N.Y.

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.]

TEDMED: Mariana Figueiro - May 5, 2015
How can we harness the power of light to improve health? Mariana Figueiro, Light & Health Program Director at the Lighting Research Center, explains in her TEDMED talk. Watch the video. For more information, also see Dr. Figueiro's TEDMED guest blog post.

Light Therapy for Better Sleep
Sleep Review - May 4, 2015
The benefits of lighting that helps us sleep, improves our mood, reduces depression, or makes us feel more alert on the job are, simply put, priceless.

Finally: Sunlight in the Office Cubicle
The Wall Street Journal - March 2, 2015
James Hagerty interviews Russ Leslie for this article on daylighting in office buildings.

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.

Let there be light: Helping people through dark days
BBC News - February 14, 2015
The Lighting Research Center at Rensselaer Polytechnic Institute is developing a system that could transform people's homes and lives by regulating the amount of light to which they are exposed. At its heart is a device known as a Daysimeter, which was developed by a team led by Professors Mark Rea and Mariana Figueiro.

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.

Electric Lighting Will Improve Our Quality of Life in the Future
NEMA ei - February 2015
LRC Director Mark Rea discusses how a 24-hour lighting scheme could improve health and productivity.

Swedish school hopes bright classroom lights boost student performance
Lux Review - January 27, 2015
A school in the far north of Sweden may have found a way to boost students' performance in the dead of winter: Stimulate them with bright, intense classroom lighting. That makes sense to Dr. Mariana Figueiro of the Lighting Research Center, who points out that a brightly lit room can act like a dose of caffeine...

Swedish school sheds light on dark days of winter
The Guardian - January 24, 2015
David Crouch interviews Mariana Figueiro for The Guardian (UK) on light & health and a school in Sweden's far north that has recently installed special lighting to improve mood, raise performance, and help students through a long, dark winter.

Driven: In search of one of the most brilliant minds in lighting
Total Lighting (TL) magazine - November 2014
Mariana Figueiro is featured in this Q+A with TL magazine editor Gillian Anderson.

Five ways to use light to improve health and sleep
BBC Mundo - November 6, 2014
Alejandra Martins interviews Mariana Figueiro for BBC Mundo (BBC Latin America).

Time to Switch Off?
BBC Focus - November 2014
You probably spend more time staring at a screen than you think. But is it bad for you? BBC's Holly Cave interviews light & health expert Mariana Figueiro.

Out of the shadows: the impacts of light on human health
Lighting Newswire - September 2014
Mariana Figueiro's Light & Health research is featured in this article by Claire Thompson. Part 1 of a two-part series exploring light's effect on human health.

The Secret to An Afternoon Energy Boost: Red Lighting
The Wall Street Journal - May 2013
Many people experience a period of reduced alertness in the afternoon, what researchers call the post-lunch dip. Exposing people to red lighting may improve their energy during this period, according to a study in Physiology & Behavior.

Lighting Up the Aviation Industry
Rensselaer Alumni Magazine - Fall 2012
Using the right light for the right time of day can enhance a person's comfort level and alertness. Use the wrong lighting, however, and a passenger's favorable flying experience could fly out the window.

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








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