Blue light

Blue light exposure during the day immediately improves alertness and performance.

Brigham and Women’s Hospital (BWH) researchers have found that exposure to short-wavelength (blue) light, which is abundant in daylight, 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,” says Shadab Rahman, PhD, a researcher in BWH’s Division of Sleep and Circadian Disorders and the study’s lead author. “These findings demonstrate that prolonged blue light exposure during the day has an alerting effect.”

To determine which wavelengths of light were most effective in warding off fatigue, the BWH researchers teamed with George Brainard, PhD, a professor of neurology at Thomas Jefferson University, who developed the specialized light equipment used in the study. During a 6.5 hour period, one group of study participants was continuously exposed to blue light while a comparison group was exposed to an equal amount of medium-wavelength (green) light. Throughout the exposure period, brain electrical activity was monitored, reaction times were measured, and participants were asked to rate how sleepy they felt.

The researchers subsequently found that participants exposed to blue light consistently rated themselves as less sleepy, had quicker reaction times, and had fewer attention lapses during performance tests as compared to those who were exposed to green light. The subjects exposed to blue light also showed changes in brain activity patterns that indicated greater alertness.

“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,” explains BWH neuroscientist and study senior investigator Steven Lockley, PhD. “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.”

It’s also important to note that the alerting effects of light can also be disruptive. Exposure to electric light in the evening – and blue light in particular, which is emitted from laptops, iPads, and smart phones – can lead to an undesired shift in the timing of the circadian body clock and alert the brain. This can lead to poor sleep quality and duration, which, in turn, increases a person’s risk for a variety of diseases.

With these nuances in mind, researchers note that the next big challenge is to figure out how to deliver better lighting. While natural light is ideal, many people do not have access to daylight in their schools, homes, or workplaces. In addition to improvements in daylight access, the advent of new, more-controllable lighting technologies may help enable researchers to design “smart” lighting systems that maximize the beneficial effects of light – and minimize negative effects – for human health, productivity, and safety.

This research was supported by the NASA-funded National Space Biomedical Research Institute, and the findings were published in the February issue of Sleep.

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