Light
What’s blue light, you ask? There’s no trick; it’s what we see as blue. As I wrote in Plants Fluoresce for Bugs, light wavelengths that humans can normally see range from blue, at the short end, through green, up through red at the long end.
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| Transparent blue light bulb (from www.1000bulbs.com) |
Short? Long? Light wavelengths are commonly measured in nanometers (nm), one of which is one billionth of a meter (i.e., nanometers are really, really short). Nominally, blue light is 400 to 500 nm, green light is 500 to 600 nm and red light is 600 to 700 nm. Combined in equal amounts, blue, green and red light (not pigments) produce what we see as white light. In case you’re wondering, sunlight has more green and less red and blue.
Old News about Blue Light
Studies have repeatedly shown that exposure to any light at nighttime can be good if you’re trying to stay awake and bad if you’re trying to sleep. Exposure to nighttime light plays havoc with your circadian rhythm--the internal clock that says you should be sleeping at night and awake during the day. That, in turn, can lead to significant health problems.
It’s suspected that the response to light is caused by a reduction in the hormone melatonin, whose release is suppressed by exposure to even a dim light. When researchers looked closer, they found that exposure to blue wavelengths had a much greater effect on melatonin suppression than other light wavelengths.
New News about Blue Light
Extending earlier studies of nighttime response, collaborators from Brigham and Women’s Hospital, Harvard Medical School, Germany’s Institute of Aerospace Medicine and Thomas Jefferson University investigated the effects of exposure to shorter light wavelengths during daytime.
They exposed 16 healthy adults, average age about 24, to either blue (460 nm) or green (555 nm) light for 6.5 hours in the middle of a 16 hour period of daytime wakefulness.
To gauge the effects, test participants did a self assessment of how sleepy they felt, their reaction times were measured, and their brains were monitored during the light exposure via an electroencephalogram (EEG). The results were also compared to those of 16 other participants who had completed the same testing at night.
The findings showed that participants exposed to blue light, both daytime and nighttime, reacted faster with fewer attention lapses and their brain patterns indicated greater alertness. Although sleepiness ratings were similar for daytime exposures to blue or green, participants exposed to blue light at night reported significantly reduced sleepiness and their alertness approached daytime levels.
Wrap Up
If I can’t find a blue light bulb for my coffee-replacement experiment, I can probably use a compact fluorescent or LED bulb. Those produce higher levels of blue light than the incandescent bulbs. Or I guess I could just sit in front of my desktop computer. Those displays give off a lot of blue light.
Hmmm…I already sit in front of my computer display for too many hours. Maybe I’ll skip the experiment today and enjoy my coffee in the morning. Thanks for stopping by.
P.S.
Publication of recent research in Sleep journal:
www.journalsleep.org/ViewAbstract.aspx?pid=29311
Articles on research on Science Daily and Medical Daily websites:
www.sciencedaily.com/releases/2014/02/140203191841.htm
www.medicaldaily.com/blue-light-improves-alertness-and-performance-during-day-even-though-it-reduces-sleep-night-268612
Articles on earlier studies in Harvard Health Letter and Daily Mail:
www.health.harvard.edu/newsletters/Harvard_Health_Letter/2012/May/blue-light-has-a-dark-side/
www.dailymail.co.uk/health/article-2470513/Lights-effect-sleep-suggested-new-research.html
Light bulb comparison in Popular Mechanics:
www.popularmechanics.com/technology/gadgets/tests/incandescent-vs-compact-fluorescent-vs-led-ultimate-light-bulb-test#slide-1
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