E-readers harm sleep quality, study finds
Users of light-emitting devices are less rested than those who stick to traditional books
Your bedtime e-reader habit may be robbing you of sleep rather than helping you drift off, a US study has found.
Light emitted by devices such as the Kindle Fire, Nook Colour and iPad affected the body's release of the sleep hormone melatonin, the study by researchers at Pennsylvania State University found.
"Electronic devices emit light that is short-wavelength-enriched light, which has a higher concentration of blue light," said Anne-Marie Chang, assistant professor of biobehavioural health at Penn State.
"This is different from natural light in composition, having a greater impact on sleep and circadian rhythms," Chang said.
The study, published in the latest edition of the Proceedings of the National Academy of Science, observed the sleep patterns of 12 adults over two weeks to compare their sleep when they read from an iPad to reading a printed book at night.
Researchers found participants took almost 10 minutes longer to fall asleep after reading from light-emitting iPads than they did after reading a conventional book.
Participants also had a lower amount of REM, or rapid eye movement, sleep after reading from iPads.