The use of a light emitting electronic device in the hours before bedtime can adversely impact us, a new study has found. Results show that blue light emitted by e-readers interrupts the body's natural circadian rhythm. This in turn causes reduced melatonin secretion, longer times to fall asleep and reduced next morning alertness. The study conducted by Brigham and Women's Hospital (BWH) who compared the biological impacts of reading a regular book to a book that had a back-lit screen. The findings were presented in the Proceedings of the Academy of Sciences on December 22, 2014. 

During the two week study, participants read either from a backlit e-reader or a regular printed book. Participants reading the e-reader took longer to fall asleep, were less sleepy in the evening and spent less time in REM sleep. In addition, the participants had reduced melatonin levels - a hormone that is normally associated with darkness and sleep. 

"Use of a light-emitting electronic device (LE-eBook) in the hours before bedtime can adversely impact overall health, alertness, and the circadian clock which synchronizes the daily rhythm of sleep....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. 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..."

A number of factors have been linked with loss of sleep including: depression, increased risk of breast cancer, colorectal cancer and prostate cancer. 

For more information: 

Brigham and Women's Hospital. "Light-emitting e-readers before bedtime can adversely impact sleep." ScienceDaily. ScienceDaily, 22 December 2014. <www.sciencedaily.com/releases/2014/12/141222131348.htm>.