Red light helps ward off 'post-lunch laziness'

Dozing off post lunch? Now sleepy drivers and lazy workers can boost their performance by exposing themselves to red light.
Exposure to certain wavelengths and levels of light has the potential to increase alertness during the post-lunch dip - mid-afternoon hours typically occurring from 2-4 pm, a new research has found.
The post-lunch dip occurs about 16-18 hours after an individual's bedtime from the previous night and more incidents and performance failures, such as automobile accidents, occur in the mid-afternoon hours.
The study by Mariana Figueiro from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute and LRC doctoral student Levent Sahin lays the groundwork for the possible use of tailored light exposures as a non-pharmacological intervention to increase alertness during the daytime.

Researchers 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.

They hypothesised 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, participants experienced two experimental lighting conditions in addition to darkness.
Long-wavelength "red" light and short-wavelength "blue" light were delivered to the corneas of each participant by arrays of light emitting diodes (LEDs) placed in 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, according to the study published in Physiology & Behaviour journal.
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.