FRIDAY, Feb. 3, 2006 (HealthDay News) -- New research suggests exposure to blue light could be just the ticket for shift workers who need to stay alert during the wee hours.
Subjects who sat in front of a lamp emitting blue light for more than six hours at night had better reaction times and felt less sleepy than those exposed to green light, scientists report.
The findings show that "different colors of light can be used to change your alertness level, but blue light is better," said lead researcher Steven Lockley, a neuroscientist at Brigham & Women's Hospital in Boston.
Over the past few years, scientists have developed greater insight into how light affects sleep. According to Lockley, they've found there are light receptors in the eye that have nothing to do with vision -- they work even in blind people.
These receptors let us know when it's daytime and nighttime so our body clocks can adjust themselves. "Light is the major cue for enhancing wakefulness," said sleep researcher Dr. Robert Vorona, an associate professor of internal medicine at Eastern Virginia Medical School in Norfolk.
In the new study, Lockley and his colleagues recruited eight men and eight women, all in their late teens and 20s, and adjusted their body clocks so they'd sleep from 10 a.m.-6 p.m., as if they were working late shifts.
The researchers then attached brain monitoring devices to the subjects and had them sit in front of specially designed blue and green lights for 6.5 hours straight. The subjects weren't allowed to do anything except sit and stay awake during the experiments, Lockley said.
As reported in the February issue of Sleep, subjects exposed to blue light -- which has shorter wavelengths -- said they were less sleepy and did better on reaction-time tests than those who sat in front of green lights. Brain scans also suggested that they were more alert.
The findings suggest that it's possible to use blue light to make workers feel alert and perform well for the duration of an entire night shift, Lockley said.
How does it work? Blue light appears to do a better job of fooling the mind into thinking that it's daylight, Lockley said. The visual apparatus of the eye is more sensitive to green light, suggesting that the blue light works by hitting the day/night receptors.
Vorona said the findings are interesting, but cautioned that the study is small.
"This may allow us to better understand the central nervous system processes that control wake and sleep," he said. In addition, the findings could provide guidance to engineers as they create lighting systems for homes and workplaces.
For now, the research provides support for manufacturers of light boxes that use blue light, Lockley said. People use the boxes to combat sleepiness and seasonal affective disorder (SAD), which can causes some people to become depressed in the darker days of winter.
But, just like ultraviolet wavelengths, blue light can be dangerous to the eyes in heavy doses, Lockley warned, so it should be used with caution.
More information
Learn more about SAD at the U.S. National Mental Health Association.
