A new study shows that iPads and other reading devices that have an integrated back light emit a type of wavelength that is shorter than the light reflected by a regular book or even an e-ink reader. Scientists found that shorter wavelengths block the release of a hormone that helps people fall asleep faster and wake up easier in the morning.
The study was conducted by a research team at Brigham and Women’s Hospital, in Boston and it was published in the journal Proceedings of the National Academy of Sciences.
Researchers say that the back-light emitted by most of the electronic devices people use to read before bedtime disrupts their circadian clock preventing them from quickly falling asleep and waking up early in the morning.
Previous researches showed that the circadian clock was also disrupted by bad habits before bedtime such as watching TV and working on a computer. But the blue light emitted by backlit reading devices is even more dangerous for melatonin release.
Sleep researchers have long warned that watching TV, working on a computer and other activities involving artificial light in the evening can disrupt sleep patterns. But the type of short-wavelength enriched light, also known as blue light, that many backlit devices emit is especially powerful at suppressing the release of melatonin, the hormone that helps bring on sleep, experts say.
Many people read things to help them fall asleep. They probably don’t realize that this technology is actually making them less likely to feel sleepy,”
Dr Charles Czeisler, lead author of the study and circadian disorders expert, said about backlit e-readers and similar devices.
The study was conducted on 12 adults over 14 days. The study participants had to read for four hours either from an iPad or from a printed book before going to bed. The bedtime was set by researchers at 10:00 p.m. After 5 days they swapped devices.
After two weeks, the study revealed that those reading from an iPad required an additional 10 minutes to fall asleep, while their REM sleep was severely disturbed. The blood tests showed that melatonin levels dropped and delayed circadian clock by one hour. Researchers believe that if it weren’t for the enforced bedtime, the delay would have been even longer.
During the study, researchers used only iPad devices, but previous researches showed that iPhones, iPods, Kindle Fire, Nook Color and other backlit devices emitted similar short wavelength blue light.
However, the original Kindle doesn’t affect sleep patterns since it uses a special e-ink technology that doesn’t require the backlit feature.
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