Use of a light-emitting electronic book (LE-eBook) in the hours before bedtime can adversely impact overall health, alertness and the circadian clock, which synchronizes the daily rhythm of sleep to external environmental time cues, according to Harvard Medical School researchers at Brigham and Women’s Hospital. These findings of the study that compared the biological effects of reading an LE-eBook to a printed book are published in the Proceedings of the National Academy of Sciences on December 22, 2014.
“We found the body’s natural circadian rhythms were interrupted by the short-wavelength enriched light, otherwise known as blue light, from these electronic devices,” said Anne-Marie Chang, corresponding author and associate neuroscientist at Brigham and Women’s Division of Sleep and Circadian Disorders. “Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock and reduced next-morning alertness than when reading a printed book.”
More here – Harvard Medical School