Researchers from Brigham and Women's Hospital (BWH), US, have found that exposure to short wavelength, or blue light, during the biological day directly and immediately improves alertness and performance.
"Our previous research has shown that blue light is able to improve alertness during the night, but our new data demonstrates that these effects also extend to daytime light exposure," said Shadab Rahman, lead author of the study.
"These findings demonstrate that prolonged blue light exposure during the day has an alerting effect," said Rahman.
Researchers compared the effects of blue light with exposure to an equal amount of green light on alertness and performance in 16 study participants for 6.5 hours over a day.
Participants then rated how sleepy they felt, had their reaction times measured and wore electrodes to assess changes in brain activity patterns during the light exposure.
Researchers found that participants exposed to blue light consistently rated themselves as less sleepy, had quicker reaction times and fewer lapses of attention during the performance tests compared to those exposed to green light.
"These results contribute to our understanding of how light impacts the brain and open up a new range of possibilities for using light to improve human alertness, productivity and safety," said Steven Lockley, senior investigator of the study.
"While helping to improve alertness in night workers has obvious safety benefits, day shift workers may also benefit from better quality lighting that would not only help them see better but also make them more alert," said Lockley.
The findings are published in the journal Sleep.