Featured Research

from universities, journals, and other organizations

Red light increases alertness during 'post-lunch dip'

Date:
April 22, 2013
Source:
Rensselaer Polytechnic Institute (RPI)
Summary:
Acute or chronic sleep deprivation resulting in increased feelings of fatigue is one of the leading causes of workplace incidents and related injuries. More incidents and performance failures, such as automobile accidents, occur in the mid-afternoon hours known as the “post-lunch dip.” A new study shows that exposure to certain wavelengths and levels of light has the potential to increase alertness during the post-lunch dip.

Long-wavelength “red” light (λmax = 630 nanometers) and short-wavelength “blue” light (λmax = 470 nanometers) were delivered to the corneas of each participant by arrays of light emitting diodes (LEDs) placed in 60 60 60 cm light boxes.
Credit: Image courtesy of Rensselaer Polytechnic Institute (RPI)

Acute or chronic sleep deprivation resulting in increased feelings of fatigue is one of the leading causes of workplace incidents and related injuries. More incidents and performance failures, such as automobile accidents, occur in the mid-afternoon hours known as the "post-lunch dip." The post-lunch dip typically occurs from 2-4 p.m., or about 16-18 hours after an individual's bedtime from the previous night.

Related Articles


A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to certain wavelengths and levels of light has the potential to increase alertness during the post-lunch dip. The research was a collaboration between Mariana Figueiro, LRC Light and Health Program director and associate professor at Rensselaer, and LRC doctoral student Levent Sahin. Results of the study titled "Alerting effects of short-wavelength (blue) and long-wavelength (red) lights in the afternoon," were recently published in Physiology & Behavior journal.

The collaboration between Figueiro and Sahin lays the groundwork for the possible use of tailored light exposures as a non-pharmacological intervention to increase alertness during the daytime. Figueiro has previously conducted studies that show that light has the potential to increase alertness at night. Exposure to more than 2500 lux of white light at night increases performance, elevates core body temperature, and increases heart rate.

In most studies to date, the alerting effects of light have been linked to its ability to suppress melatonin. However, results from another study led by Figueiro demonstrate that acute melatonin suppression is not needed for light to affect alertness during the nighttime. They showed that both short-wavelength (blue) and long-wavelength (red) lights increased measures of alertness but only short-wavelength light suppressed melatonin. Melatonin levels are typically lower during the daytime, and higher at night.

Figueiro and Sahin hypothesized that if light can impact alertness via pathways other than melatonin suppression, then certain wavelengths and levels of light might also increase alertness during the middle of the afternoon, close to the post-lunch dip hours.

During the study conducted at the LRC, participants experienced two experimental lighting conditions in addition to darkness. Long-wavelength "red" light (λmax = 630 nanometers) and short-wavelength "blue" light (λmax = 470 nanometers) were delivered to the corneas of each participant by arrays of light emitting diodes (LEDs) placed in 60 60 60 cm light boxes. Participant alertness was measured by electroencephalogram (EEG) and subjective sleepiness (KSS scale).

The team found that, compared to remaining in darkness, exposure to red light in the middle of the afternoon significantly reduces power in the alpha, alpha theta, and theta ranges. Because high power in these frequency ranges has been associated with sleepiness, these results suggest that red light positively affects measures of alertness not only at night, but also during the day. Red light also seemed to be a more potent stimulus for modulating brain activities associated with daytime alertness than blue light, although they did not find any significant differences in measures of alertness after exposure to red and blue lights. This suggests that blue light, especially higher levels of blue light, could still increase alertness in the afternoon. It appears that melatonin suppression is not needed for light to have an impact on objective measures of alertness.

"Our study suggests that photoreceptors other than the intrinsically photosensitive retinal ganglion cells respond to light for the arousal system," said Figueiro. "Future research should look into the spectral sensitivity of alertness and how if it changes over the course of 24 hours."

Sahin, who has more than 10 years of experience in railway engineering, was interested in this study from a transportation safety perspective, and what the results could mean to the transportation industry. "Safety is a prerequisite and one of the most important quality indicators in the transportation industry," said Sahin. "Our recent findings provided the scientifically valid underpinnings in approaching fatigue related safety problems in 24 hour transportation operations."

From the present results, it is not possible to determine the underlying mechanisms contributing to light-induced changes in alertness because the optical radiation incident on the retina has multiple effects on brain activity through parallel neural pathways. According to Figueiro, that is an area that she would like to explore in future research.

The study was funded by the Office of Naval Research.


Story Source:

The above story is based on materials provided by Rensselaer Polytechnic Institute (RPI). Note: Materials may be edited for content and length.


Journal Reference:

  1. Levent Sahin, Mariana G. Figueiro. Alerting effects of short-wavelength (blue) and long-wavelength (red) lights in the afternoon. Physiology & Behavior, 2013; 116-117: 1 DOI: 10.1016/j.physbeh.2013.03.014

Cite This Page:

Rensselaer Polytechnic Institute (RPI). "Red light increases alertness during 'post-lunch dip'." ScienceDaily. ScienceDaily, 22 April 2013. <www.sciencedaily.com/releases/2013/04/130422100801.htm>.
Rensselaer Polytechnic Institute (RPI). (2013, April 22). Red light increases alertness during 'post-lunch dip'. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/2013/04/130422100801.htm
Rensselaer Polytechnic Institute (RPI). "Red light increases alertness during 'post-lunch dip'." ScienceDaily. www.sciencedaily.com/releases/2013/04/130422100801.htm (accessed October 25, 2014).

Share This



More Health & Medicine News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

IKEA Desk Converts From Standing to Sitting With One Button

IKEA Desk Converts From Standing to Sitting With One Button

Buzz60 (Oct. 24, 2014) IKEA is out with a new convertible desk that can convert from a sitting desk to a standing one with just the push of a button. Jen Markham explains. Video provided by Buzz60
Powered by NewsLook.com
Ebola Protective Suits Being Made in China

Ebola Protective Suits Being Made in China

AFP (Oct. 24, 2014) A factory in China is busy making Ebola protective suits for healthcare workers and others fighting the spread of the virus. Duration: 00:38 Video provided by AFP
Powered by NewsLook.com
WHO: Millions of Ebola Vaccine Doses by 2015

WHO: Millions of Ebola Vaccine Doses by 2015

AP (Oct. 24, 2014) The World Health Organization said on Friday that millions of doses of two experimental Ebola vaccines could be ready for use in 2015 and five more experimental vaccines would start being tested in March. (Oct. 24) Video provided by AP
Powered by NewsLook.com
Doctor in NYC Quarantined With Ebola

Doctor in NYC Quarantined With Ebola

AP (Oct. 24, 2014) An emergency room doctor who recently returned to the city after treating Ebola patients in West Africa has tested positive for the virus. He's quarantined in a hospital. (Oct. 24) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins