Is blue light really special? A new study says that exposure to shortwave light, which appears blue, immediately improves alertness and performance.
Researchers at Brigham and Women's Hospital and Harvard Medical School compared the effects of blue light and green light on volunteers during the night. Subjects exposed to blue light rated themselves as less sleepy, had quicker reaction times and had fewer lapses in attention than those exposed to green light. They also had changes in their brain activity patterns that indicated a more alert state.
Researchers say the findings, published in today's issue of the journal Sleep, open up a new range of possibilities for using light to improve people's health.
"Subjects exposed to blue light were able to sustain a high level of alertness during the night when people usually feel most sleepy, and these results suggest that light may be a powerful countermeasure for the negative effects of fatigue for people who work at night," said Dr. Steven Lockley, the lead author of the study and a researcher in Brigham and Women's Hospital's Division of Sleep Medicine.
Lockley said the results could help those who need to sustain alertness for long periods of time, such as long-distance drivers, pilots or astronauts, as well as shift workers.
Eye Used for More Than Sight
Until recently, it was thought that the eye was simply used to see objects. Brigham and Women's Hospital's researchers and others have shown that it is also used to detect light for other purposes, such as resetting the body clock to the 24-hour day. This photoreceptor system is different from that used in normal vision as it has a different sensitivity to the color of light and is retained in some totally blind people.
But several sleep specialists say that therapeutic use of blue light needs more study.
"It is of potential interest and may be applicable to shift work and jet lag," said Phyllis C. Zee, director of the Sleep Disorders Center at Northwestern University Feinberg School of Medicine. "Because these are preliminary research, performed in controlled settings, it is important to also note that further work needs to be performed to determine the safety of prolonged use of short wavelength light in humans."
If misused, blue light can cause damage to the eye and exposure needs to be monitored, Lockley said, but this new research holds promise.
"With the advent of new, more controllable lighting technologies, we can begin to develop 'smart' lighting systems designed to maximize the beneficial effects of light for human health," he said.