 Basking in the blue glow of iPads, smartphones and other electronic devices before bedtime could be messing up our sleep patterns more profoundly than we realize, and even affecting our long-term health, according to a new study published Monday in the Proceedings of the National Academy of Sciences. Czeisler and colleagues, including lead researcher Anne-Marie Chang, an associate neuroscientist in the division of sleep medicine at Harvard Medical School, recruited a small group of people for an intensive experiment. "It may be having a greater impact than we previously thought," said Anne-Marie Chang, a professor at Penn State University and a co-author of the study, which was conducted at Brigham and Women's Hospital in Boston. During a two-week inpatient experiment involving a dozen adults, some participants were asked to read on an iPad for four hours each night before bedtime, for five consecutive nights. When subjects read on the iPad as compared to the paper books (hereafter referred to as "books"), the people reported feeling less sleepy at night and less alert the following morning. But, empirically, they also took longer to fall asleep on the iPad nights and spent less time in the REM phase of sleep. Chang told me they all emitted similar patterns, enriched for short-wavelength blue light, and at a similar intensity.
– Your iPad or smartphone could well be hurting your sleep patterns, even if you're getting in a full eight hours of shuteye, researchers say—and the effects could be long-term. Over a five-night period, researchers in Boston had some subjects read for four hours a night on an iPad; others did their reading on printed books, with the lights low, the Washington Post reports. Among members of the iPad group, levels of melatonin, a chemical behind sleepiness, decreased. It took them longer to drift off by an average of 10 minutes, the Wall Street Journal reports. And once they did, their periods of rapid eye-movement sleep were shorter. The effects weren't limited to the nighttime. Their circadian rhythms were affected, and the next day—even if they'd slept eight hours—they reported being more tired. And in the long term, reduced melatonin may boost the risk of various forms of cancer (prompting the rather frightening headline "Reading an iPad in Bed May Increase Cancer Risk," the Atlantic notes). At issue is what's known as "blue light," the kind often given off by backlit gadgets, the Journal adds. "We introduce these devices that have medical and biological effects without requiring any health studies on their impact ... They don't have to go through any evaluation like a drug would, for safety and efficacy," says a researcher. "I think it's time to rethink that." (As far as sleep goes, here's your "optimal" amount.)