Blue light may fight fatigue around the clock

Researchers from Brigham and Women’s Hospital (BWH) have found that exposure to short wavelength, or blue light, during the biological day directly and immediately improves alertness and performance. These findings are published in the February issue of Sleep.

"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, PhD, a researcher in BWH’s Division of Sleep Medicine and lead author of this study. "These findings demonstrate that prolonged blue light exposure during the day has an an alerting effect."

In order 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. Researcherscompared 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.

The 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 who were exposed to green light. They also showed changes in brain activity patterns that indicated a more alert state.

"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," explained Steven Lockley, PhD, neuroscientist at BWH and 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."

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 work places. In addition to improvements in daylight access, the advent of new, more controllable lighting technologies may help enable researchers to develop ‘smart’ lighting systems designed to maximize the beneficial effects of light for human health, productivity and safety.

Study links exposure to light at night to depression, learning issues

For most of history, humans rose with the sun and slept when it set. Enter Thomas Edison, and with a flick of a switch, night became day, enabling us to work, play, and post cat and kid photos on Facebook into the wee hours.

However, according to a new study led by a Johns Hopkins biologist, this typical 21st- century scenario comes at a serious cost: When people routinely burn the midnight oil, they risk suffering depression and learning issues, and not only because of lack of sleep. The culprit could also be exposure to bright light at night from lamps, computers, and even iPads.

"Basically, what we found is that chronic exposure to bright light—even the kind of light you experience in your own living room at home or in the workplace at night if you are a shift worker—elevates levels of a certain stress hormone in the body, which results in depression and lowers cognitive function,” said Samer Hattar, a biology professor in the Krieger School of Arts and Sciences.

The study, published in the Nov. 14 Advance Online Publication of the journal Nature, used mice to demonstrate how special cells in the eye (called intrinsically photosensitive retinal ganglion cells, or ipRGCs) are activated by bright light, affecting the brain’s center for mood, memory, and learning.