How E-books May Disrupt Your Sleep

By NICHOLAS BAKALAR DECEMBER 22, 2014 3:00 PM December 22, 2014 3:00 pm

Planning to read in bed tonight? It may be better to read an actual book instead of an e-book reader. A small study has found that reading light-emitting electronic devices before bedtime is a recipe for poor sleep.

Researchers randomly assigned 12 healthy young adults to one of two activities: reading a light-emitting e-book in a dimly lit room for about four hours before bedtime on five consecutive evenings, or reading a printed book for the same amount of time. All participants did both tasks.

The researchers took blood samples to measure melatonin levels, and electronically tracked how long it took to fall asleep and how much time was spent in each sleep stage. The study, done at Brigham and Women’s Hospital in Boston, is online in the Proceedings of the National Academy of Sciences.

Compared with a printed book, a light-emitting e-book decreased sleepiness, reduced REM sleep (often called dream sleep), and substantially suppressed the normal bedtime rise of melatonin, the hormone that regulates the sleep and wake cycle. The e-book users took longer to fall asleep and felt sleepier in the morning.

“Much more has to be known about the kind of impact these devices have on our health and well-being,” said the lead author, Anne-Marie Chang, an assistant professor of biobehavioral health at Penn State. “The technology moves quickly, and the science lags.”