Curling up with a good book might be a better idea than an electronic device in bed, according to a limited study conducted at Brigham and Women’s Hospital in Boston.
The researchers, who published their findings online in the Proceedings of the National Academy of Sciences, concluded that the use of e-books may disturb sleep patterns. They enlisted 12 healthy young adults, who read either e-books or printed books in poorly lighted rooms for about four hours before bedtime for five straight nights. Each participant was tracked while performing both tasks. The e-books were set on maximum brightness.
Blood samples were drawn to detect levels of melatonin, a hormone that regulates sleep, the New York Times reported. The researchers wrote that “participants reading a (light-emitting) e-book 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.”
The Times, in its “Well” blog, noted that the volunteers who used Apple iPads took an average of 10 minutes longer to fall asleep. They got less rapid eye movement, or “dream,” sleep. The scientists wrote that the results have “important implications for understanding the impact of such technologies on sleep, performance, health and safety.”
The lead author of the report was Anne-Marie Chang, assistant professor of biobehavioral health at Penn State. She told the Times that “much more has to be known about the kind of impact these devices have on our health and well-being.” She pointed out that “the technology moves quickly, and the science lags.”
Previous sleep studies suggested that watching television, working on a computer or using other devices with artificial lights in the evening can affect sleep patterns, according to a Wall Street Journal story. “The type of short-wavelength enriched light, also known as blue light, that many backlit devices emit is especially powerful at suppressing the release of melatonin,” the story stated.
Blue light shining into the eyes “is exactly what you don’t want to do at bedtime,” said Charles Czeisler, the study’s senior author (and head of the Boston hospital’s division of sleep and circadian disorders). “Many people read things to help them fall asleep. They probably don’t realize that this technology is actually making them less likely to feel sleepy.”
The Journal reported that “although the study used only iPads, in separate tests the researchers found that iPhones, iPods, the Nook Color and the Kindle Fire all had similar short-wavelength emissions.” The original Kindle, which lacks its own light source, reflects the same amount of ambient light as a printed book.
The study, funded by the National Institutes of Health, did not test the Kindle Paperwhite or the Kindle Voyage. The manufacturer of those devices, Amazon, claims that they employ “a different front-lighting technology designed to be easier on the eyes.”
On many e-books, the screen’s brightness can be adjusted. Readers of certain devices have the option of reading white words on a black background, which some experts believe to be less harmful to sleep. The study did not test the theory.
The researchers explained that “the use of light-emitting electronic devices for reading, communication and entertainment has greatly increased recently”; and that “in the past 50 years, there has been a decline in average sleep duration and quality, with adverse consequences on general health.”
A recent survey involved 1,508 U.S. adults. Ninety percent of them said they operated some sort of electronic device at least a few nights a week during the hour before they went to sleep.
The use of e-books continues to increase, despite “mounting evidence from countries around the world (revealing) the negative impact of such technology on sleep,” according to the researchers in Boston.