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A dim blue light in the car may keep sleep-deprived drivers alert at night and reduce mistakes as effectively as caffeine, new research suggests.
"Recent studies demonstrated that (circadian rhythms) and brain areas involved in the regulation of arousal are sensitive to short-wavelength radiation. The advantage of using blue light to fight nocturnal sleepiness is its very low intensity compared to white light, (so it) can be then used in a car without distracting the driver," Dr Jacques Taillard said.
Dr Taillard, a neuroscientist at Université Bordeaux 2 in Bordeaux, France, presented his group's findings at the annual meeting of the Associated Professional Sleep Societies in Boston, Massachusetts.
The researchers enrolled 48 drivers and subjected each one to three different tests, all on the same two-lane highway in the middle of the night. Each test was separated from the others by at least a week.
Tests done in the morning
The participants drove for 250 miles (400 km), from 1:00 am to 5:15 am with a 15-minute break halfway through. In one test, the drivers had a dim, 20 lux GOLite (Philips) shining in the vehicle (460nm wavelength). By comparison, twilight can be about 10 lux and a lighted hallway might be 80 lux.
In the other two tests, drivers took either two 200mg doses of caffeine, or a caffeine placebo.
Eight drivers opted out of the blue light test, however, complaining that it was distracting, and were excluded from the analysis.
The primary outcome was the number of times the drivers inappropriately crossed lines in the road. In the placebo trial, drivers crossed lines an average of 26.42 times. With caffeine, they averaged 12.51 line crossings (p=0.001). And with blue light in the car, they had a mean of 14.58 (p=0.003).
Too soon to instal blue lights
"(The) non-inferior efficacy of continuous nocturnal blue light exposure compared with caffeine suggests that this in-car countermeasure could be used to fight nocturnal sleepiness at the wheel," the research team wrote in its abstract for the meeting.
As can be expected, all of the drivers were much more likely to cross lines in the second half of the trip than in the first. And none of the interventions appeared to affect the drivers' sleep after they finished the tests.
This evidence notwithstanding, it may be too soon to instal blue lights in cars, however.
Dr Raman Malhotra, who co-directs the SLUCare Sleep Disorders Centre at Saint Louis University in Saint Louis, Missouri, and was not involved in this research, noted in an email to Reuters Health that "blue light (and light boxes in general) have been used to help with alertness," and this research "did show that blue light acted as a countermeasure to combat sleepiness with driving."
Don’t drive if you sleepy
"This can be considered by drivers, though countermeasures such as caffeine have more data and even in this study seemed to work at least as well," Dr Malhotra said.
He added, "Ultimately, the best advice is to not drive at all if you are sleepy, because even with countermeasures, it can still be dangerous."
"This study tested the effect of occasional continuous nocturnal blue light exposure," Dr Taillard said. "Future studies should investigate the effect of continuous nocturnal blue light exposure used repeatedly."
In the meantime, he warned, the blue lights can be hazardous if not installed correctly. "The light device must be tested for ocular safety," he said, "and the implementation (place on the dashboard or above the driver's head) in the car must be performed by a specialist."
(Rob Goodier, Reuters Health, June 2012)
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