August 29, 2012
Want A Good Night Sleep? Leave The Backlit Tablet Out Of The Bedroom
Lawrence LeBlond for redOrbit.com - Your Universe Online
Electronic devices with self-illuminated backlit displays have been shown to cause melatonin levels to drop, making it much harder for persons who use such devices to read or study before bedtime to fall asleep. The findings come from a study by researchers at the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute (RPI) in Troy, NY, who explain that if you have stared at a luminous screen for a long enough period, chances are you will probably have a hard time falling asleep.
“Our study shows that a two-hour exposure to light from self-luminous electronic displays can suppress melatonin by about 22 percent,” said lead researcher Mariana Figueiro of RPI. “Stimulating the human circadian system to this level may affect sleep in those using the devices prior to bedtime.”
The small study--“Light Level And Duration Of Exposure Determine The Impact Of Self-Luminous Tablets On Melatonin Suppression”--is published in the journal Applied Ergonomics and funded by Sharp Laboratories.
The study included 13 subjects who read, watched videos and played video games on tablets with backlit displays for two hours before bedtime.
Study participants were divided into three groups. The first group viewed the tablets while wearing clear goggles fitted with 470-nm blue light from LEDs. This was a “true positive” condition because the blue light is known to be a strong stimulus for suppressing melatonin. Group 2 wore orange-tinted glasses, capable of filtering out the short-wavelength radiation that can suppress melatonin; this was the “dark control” condition. Group 3 wore no glasses.
Each tablet in the experiment was set to full brightness. In order to accurately record personal light exposures during the experiment, each subject wore a device known as a Dimesimeter close to the eye. This device, developed by LRC, continuously recorded circadian light and activity levels.
Actual melatonin suppression values after 60 minutes were very similar to those estimated using a predictive model of human circadian photo-transduction for one-hour light exposures.
“Based on these results, display manufacturers can use our model to determine how their products could affect circadian system regulation,” and possibly design more “circadian-friendly” electronic devices that could either increase or decrease circadian simulations depending on the time of day--reducing circadian stimulation in the evening for a better night's sleep, and increasing in the morning to encourage alertness.
Past studies have shown that disturbances in our circadian rhythm may lead to brain cell changes, and cause sleep problems in aging. Researchers at the University of Southern California found that circadian rhythm is much more important to life than had previously been suspected.
In the current study, melatonin suppression that occurred after exposure to the luminous tablet screen was similar to what one would expect after exposure to normal sunlight, Figueiro explained. In other words, the screen light tricks the human´s body clock into thinking it is still daytime.
The team conducted their studies using a tablet computer, but believe any gadget with a backlit display could have a similar effect, including smartphones and e-readers, with the exception of the Kindle, which has no backlight.
“Technology developments have led to bigger and brighter televisions, computer screens, and cell phones,” Brittany Wood, researcher and study coauthor, told MedicalNewsToday. “To produce white light, these electronic devices must emit light at short wavelengths, which makes them potential sources for suppressing or delaying the onset of melatonin in the evening, reducing sleep duration and disrupting sleep. This is particularly worrisome in populations such as young adults and adolescents, who already tend to be night owls.”
The results of the study suggest avoiding backlit tablets and reaching for a paperback book instead. The black-and-white Amazon Kindle is another safe bet.
But researchers also believe the study could give manufacturers ideas to build gadgets for a host of conditions and illnesses linked to lack of sunlight exposure, such as seasonal affective disorder (SAD) and sleep disorders. Users could receive therapy while watching a movie, playing a game, or even writing and reading. This would be much more therapeutic than just sitting in front of a light box, which is a treatment option for SAD patients.
MedicalNewsToday reports in its article that in prehistoric times, man was used to going to bed at dusk because melatonin levels would shoot up as sunset occurred, making these ancient people tired. And in those times, especially before fire was discovered, it made sense to go to sleep at dusk, and melatonin played a significant role in that. But then fire was discovered, then candles, light bulbs, and then LED. Now we are exposed to light at all hours of the day and night, really messing up our biological clocks.
For the time being, since there is no way to escape the omnipresence of light in our technological world, perhaps the best thing to do is to grab a good paperback, and enjoy a few less hours of light at night before bedtime.