Using light-emitting eBook readers (LE-eBook) immediately before bedtime negatively affects health, according to a recent North-American study from the Division of Sleep Medicine at Harvard Medical School. It involved 12 healthy young adults and lasted for two weeks.
Researchers concluded that the 12 participants who read light-emitting eBook readers took on average 10 minutes longer to fall asleep than the participants in the control group, who read printed books before falling asleep.
The participants who read LE-eBooks before going to sleep also showed lower levels of melatonin, a hormone that promotes sleep, and a much shorter REM sleep phase than participants reading printed books. In addition, participants reading eBooks showed reduced next-morning alertness. The study was published in the journal of the Proceedings of the National Academy of Sciences.