There’s nothing wrong with settling down with a good book at the end of day to melt away tension and help you to unwind. But if you’re picking up an e-reader or a tablet, then you’re doing it all wrong.
That’s what Anne-Marie Chang, associate professor of biobehavioral health at Penn State University, and her colleagues found when they compared digital readers with the printed word. Reporting in the Proceedings of the National Academy of Sciences, they say that people who use the electronic devices such as an iPad had more disrupted sleep patterns and were more tired the next morning than those who read from traditional books.
Chang, who conducted the study while at Brigham and Women’s Hospital, designed the trial to be as objective as possible. What Chang found was a marked difference between each participant’s sleep patterns and alertness depending on whether they read from a digital reader or from a book. When they read from an iPad, their evening levels of melatonin failed to drop as much as they should, while they remained at expected levels when they read from a book. That led to a delay in body’s biological signal to go so sleep of about an hour and a half, making the participants more alert and therefore not ready for bed.
And when the scientists looked at their sleep patterns, they found that the differences went even deeper. When the volunteers read from electronic devices, they had shorter REM sleep, the stage in which memories are consolidated and the brain refreshes itself, than when they read from printed books. This occurred even though the volunteers slept for the same amount of time, eight hours, every night.
What’s more, the effect of those differences in sleep patterns spilled over into the next morning. When they read from digital readers, the participants reported feeling sleepier and were less alert (as measured on standardized testing of alertness) than when they used books. “What was surprising to me was that we would see effects the next day. There was no difference in total sleep duration between the two conditions, but there was a significant amount of REM sleep difference,” says Chang. “This may indicate that these effects are longer term than we thought.”
Previous studies showed that one reason for the disrupted sleep linked to the electronic devices may be due to the type of light they use. It’s in the blue wavelength, and some researchers have connected this light to a disruptions in the melatonin system, similar to those Chang found in the study. She says it’s also possible that having the light shine directly into the eyes, as backlit electronic readers do, may also keep the body’s sleep signals from activating — reading lamps or room lights reflect light so aren’t as disruptive to the body’s wake-sleep cycle.
The findings hint at why sleep — getting enough, and getting good quality sleep — is becoming more a of challenge and potentially a growing health problem. “There is an easy answer but it’s not a popular one that’s easy to hear,” says Chang. “Using electronic devices is not a train that is slowing down any time soon. So the important thing is to know more about them, and how they are affecting our lives, our health and our well being.” And in the meantime, maybe put the tablet down in the hours before you go to bed. Or buy a book.