As Stephen Fry tweeted a couple of years ago: “Books are no more threatened by Kindle than stairs by elevators.” But which one threatens you?
Research at Brigham and Women’s Hospital has shown that the use of light-emitting e-readers before bed can perturb the body’s circadian cycle and overall health. While previous studies had established that the blue light emitted from electronic devices, which has shorter wavelengths and higher energy, impacts melatonin’s secretion and increases alertness, its effects on the sleep cycle were unknown.
Twelve volunteers were asked to read a printed book for four hours prior to bedtime for five successive nights and then an e-book on an iPad for another five nights, or vice versa. It was discovered that the participants who used an e-reader had difficulty falling asleep and were less alert on the following morning.
Their exposure to blue light before bed lead to shorter REM cycles and decline in melatonin secretion. Melatonin is a hormone, secreted by the pineal gland, that induces sleepiness in the evening. Its reduced levels in the study suggested that the circadian cycle of the volunteers, reading e-books, had been delayed by over an hour. Furthermore, they felt more sleepy and tired after an eight-hour sleep than the participants reading printed books.
The possibility that light-emitting electronic devices contribute to sleep deprivation calls into question the well-being of the generations, growing up with e-books, Facebook and Angry Birds. Sleep deficiency has been linked to depression, obesity and diabetes; and recent findings indicate that long-term melatonin hyposecretion might increase risk of breast cancer and prostate cancer.
http://www.pnas.org/content/early/2014/12/18/1418490112.full.pdf+html
