Kathi 2012-04-27 17:27:31
Jefferson and Brigham and Women s Researchers Find Blue Light Important
for Setting Biological Clock
Researchers from Brigham and Women s Hospital (BWH) in Boston and
Jefferson Medical College have found that the body s natural biological
clock is more sensitive to shorter wavelength blue light than it is to
the longer wavelength green light, which is needed to see.
The discovery proves what scientists have suspected over the last
decade: a second, non-visual photoreceptor system drives the body s
internal clock, which sets sleep patterns and other physiological and
This discovery will have an immediate impact on the therapeutic use of
light for treating winter depression and circadian disorders, says
George Brainard, Ph.D., professor of neurology at Jefferson Medical
College of Thomas Jefferson University in Philadelphia. Some makers of
light therapy equipment are developing prototypes with enhanced blue
In the long range, we think this will shape all artificial lighting,
whether it s used for therapeutic purposes, or for normal illumination
of workplaces, hospitals or homes this is where the impact will be,
he says. Broad changes in general architectural lighting may take
years, but the groundwork has been laid.
In theory, he says, If a clinician wants to use light therapeutically,
the blue wavelengths may be more effective. If you wanted built-in
illumination that would enhance circadian regulation, you might want
this wavelength region emphasized. It is interesting that natural
daylight the blue sky is rich in this part of the spectrum.
Dr. Brainard and his co-workers previously discovered that wavelengths
of light in the blue region of the visible spectrum are the most
effective in controlling the production of melatonin, which plays an
important role in the body s circadian rhythms.
The scientists reported their findings September 9 in the Journal of
Clinical Endocrinology and Metabolism.
In the study, researchers tested 16 healthy subjects, exposing them to
the same amount of blue or green light. They measured the effect of the
light exposure on the timing of their biological rhythms. The
researchers found that blue light was twice as effective as the same
amount of green light at resetting the internal biological clock. Dr.
Brainard, who is also associate team leader for the Human Performance
Factors, Sleep and Chronobiology Team of the National Space Biomedical
Research Institute, sees the work as having potential impact on sleep
disorders involving space travel. Sleep disorders are extremely common,
affecting as many as 40 million Americans.