Many people enjoy reading a good book in bed with a dim light, but the arrival of e-books has changed habits—and apparently, sleep quality too. A team from Harvard Medical School warns that the screens of smartphones, tablets and laptops disrupt the biological clock, causing problems when it's time to rest.
After spending more than six years working nights, I could write a thing or two about sleep problems. It all comes down to two factors: darkness and silence. The first ray of light signals it's time to get up, but for those of us who follow the vampire path, that same ray can steal sleep in minutes. Noise, on the other hand, doesn't stand a chance. Between phones, knocks, horns, traffic, and the delusional neighbor convinced he can win a Grammy playing drums, a visit from Morpheus becomes a genuine miracle. Still, many people don't realize that the main enemy of their rest could be on the nightstand.
The Experiment
A team from Harvard Medical School conducted an experiment in which twelve people spent two weeks in a "sleep laboratory". There, each member read from both a book and an iPad for four hours before going to bed, five nights in a row. The devices were set to emit maximum brightness, and "bedtime" was arbitrarily set at 10 pm. Participants who read from the iPad took on average ten minutes longer to fall asleep, and sleep monitors revealed they spent less time in REM sleep. Blood tests indicated a reduction in melatonin production, delaying the circadian rhythm by up to one hour. Those who used the tablet for reading also said they felt more awake at bedtime, but needed extra time to fully wake up the next morning.
Blue Light and Your Sleep
While the study focused on iPads, the effect also extends to other tablets, as well as Nook Color and Kindle Fire readers, smartphones, and laptops. The problem is none other than the light emitted by screens, especially blue (450 nanometers). Professor Charles Czeisler, one of the researchers, explains that this short-wavelength light reflects directly onto the user's eyes, while with a physical book, only the light on the pages is reflected. The only devices that seem to escape this dilemma are those with e-ink screens, like the original Kindles. In other words, nobody is saying you should stop reading, but if sleep doesn't come easily, it may be necessary to reduce the time spent in front of screens.
