We’ve all been there, some of us more often than others. You know what I’m talking about. That mid-afternoon moment where we find ourselves crashing at our computers. Or nodding off into our notebooks.
And it’s not just our productivity that’s affected. It turns out that acute or chronic sleep deprivation and the resulting fatigue is one of the leading causes of workplace incidents and related injuries. Most performance failures, including car accidents, occur in the mid-afternoon hours known as the “post-lunch dip.” Typically this occurs sometime between 2-4 p.m., or about 16-18 hours after the previous night’s bedtime.
Now a new study from the Lighting Research Center [who knew there was such a thing?] at Rensselaer Polytechnic Institute – the nation’s oldest technological university – suggests that there may be a way to alleviate afternoon accidents. Their research shows that exposure to certain wavelengths and levels of light have the potential to increase alertness during the post-lunch dip. These results pave the way for a non-pharmacological intervention to increase alertness during the daytime.
Mariana Figueiro, LRC Light and Health Program director, has previously conducted studies that show that light has the potential to increase alertness at night. Exposure to strong levels 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 the circadian rhythm regulating hormone – melatonin, the levels of which are typically lower during the daytime, and higher at night. However, results from a previous study by Figueiro demonstrated that acute melatonin suppression is not needed for light to affect alertness during the nighttime. While both short-wavelength (blue) and long-wavelength (red) lights increased measures of alertness, only short-wavelength light suppressed melatonin.
Based on this finding the researchers 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.
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 improves alertness.
Co-author Levent Sahin, a doctoral student at the Lighting Research Center, 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.”
Even though the present results don’t fully explain the underlying mechanisms of light-induced changes in alertness it seems we could all benefit from a little red light on our desks.