The bed must be reserved as a place for sleep and sex only. That was the decree of psychologist Richard Bootzin in his influential 1972 proposal for a "stimulus-control" approach to better sleep. One central tenet was operant conditioning: The bed must be a sanctuary, such that the brain is trained to sleep when it is in the bed. The allowance for sex—which, in its ideal form, is one of the most stimulating things a human body can experience—always seemed to me at odds with the stimulus-control approach. A note to aspiring self-help writers: The book For Better Sleep, Kitchen Sex remains unwritten. Otherwise, though, the idea of stimulus control made sense to a lot of people. It also included advice to avoid bedroom behaviors that abet anxiety, like clock-watching. And Bootzin's approach to insomnia endured, proving itself in several studies. So last year when Charles Czeisler, a professor of sleep medicine at Harvard Medical School, found that around 90 percent of Americans use some kind of electronic device within the hour before bed—and correlated the degree of use with ever-poorer sleep—one of his first theories of the case was overstimulation. That's because, Czeisler and colleagues wrote in the Journal of Clinical Sleep Medicine in December of 2013, "In addition to making phone calls, cell phones now allow the user to instant message, listen to music, send emails, play games, and surf the Internet." So they do. And all of that stimulation, the researchers proposed, may "impede the natural withdrawal of sympathetic nervous system activity necessary for sleep onset." Or, preclude one's ability to chill. To what degree is the light from a device, not the cognitive stimulation it provides, responsible for the known sleep effects of screens? A more vague hypothesis raised by Czeisler at the time was that the detrimental effects on sleep might be due to "light and electromagnetic transmissions from technological devices." Other researchers, too, have lately blamed the light exposure element, which is well understood to influence sleep patterns through photoreceptors in the retina that tell the brain to release the hormone melatonin. It flows forth from the pineal gland into the blood and around the body. Normally, melatonin levels rise before bedtime, peak in the middle of the night, and decrease in the early morning. That is why daily light-dark cycles are important for normal levels of alertness and sleep in most people. Abnormalities in these cycles are the basis for shift-work sleep disorder. But to what degree is the light from a device, not the cognitive stimulation it provides, responsible for the known sleep effects of screens? And is that light worse than, say, the light from a light bulb? In research published today in the journal Proceedings of the National Academy of Sciences, Czeisler and colleagues made an interesting advance in understanding that idea, and just how screens themselves tell our brains to stay awake. It began with the mundane observation that people read to unwind—often at night, often in bed. As far as sleep is concerned, Czeisler wondered, does it matter whether those people read books on iPads, Kindles, or paper? 
 
 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. For two weeks, participants took up residence in a monitoring unit at the clinical investigation center at Boston's Brigham and Women's Hospital. The subject group was only 12 people, but for a trial that requires so much commitment, that is not an unimpressive number. Though it was an enviable situation, in some ways: The people were allotted an idyllic eight hours for sleep, from 10:00 p.m. to 6:00 a.m.—a schedule they kept for three weeks prior, as well, in preparation. They were also allotted four hours of undisturbed reading time each night. The elements of a changing world, from technology and business to politics and culture. 
 
 Read More For five days in a row, the people read either a book or an iPad for four hours prior to sleep. Both were kept at constant, preordained distances from the person's face. Chang and colleagues monitored the people's sleep patterns with electroencephalograms all night. Each person did one stint with the iPad, and one with the book. Before and after each trial period, the people underwent hourly blood tests to paint a day-long picture of just how much melatonin was in their veins at any given time. 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. Of course, this is not a blinded study, the kind with a placebo—the participants could have been biased in reporting how they felt. But, empirically, they also took longer to fall asleep on the iPad nights and spent less time in the REM phase of sleep. And the blood tests showed that on average, the brain's melatonin secretion on those nights was delayed by an hour and a half. Though this experiment dealt exclusively with iPads, the researchers also tested the light-emission patterns of other tablets, as well as phones and laptops. Chang told me they all emitted similar patterns, enriched for short-wavelength blue light, and at a similar intensity. So she would expect similar clinical findings for any such device. ||||| 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. 
 
 "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. 
 
 A growing body of evidence has suggested what many people have experienced firsthand - that the pervasive glow of electronic gadgets can hinder a good night's sleep. But researchers behind Monday's study, which was supported by a grant from the National Institutes of Health, set out to decipher what changes in the body cause those disruptions. 
 
 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. Others read printed books in dim light. After a week, the groups switched. 
 
 Researchers found that participants using iPads displayed reduced levels of melatonin, a hormone that typically increases in the evening and helps induce sleepiness. They took longer to fall asleep, and spent less time in restorative REM, or rapid-eye movement, sleep. 
 
 In addition, the iPad readers reported being sleepier and less alert the following morning, even after eight hours of sleep. They also displayed delayed circadian rhythms. 
 
 "There's a lot of skepticism out there; a lot of people think this is psychological," said Charles Czeisler, director of the Division of Sleep Medicine at Harvard Medical School. "But what we showed is that reading from light-emitting, e-reader devices has profound biological effects." 
 
 Czeisler said that although the study used only iPads, the effect isn't unique to that device. Other products produce similar blue-light emissions, including tablets, e-readers, smartphones, laptops and LED monitors. Czeisler said the standard Kindle e-reader, which doesn't emit light, was an exception and was more akin to a printed book. (The Kindle is produced by Amazon; its chief executive, Jeff Bezos, owns the Post). 
 
 So other than a little grogginess, why should we worry about the apparent loss of sleep that our glowing screens are causing us? 
 
 Czeisler and Chang said that as electronic devices become only more prevalent, and as their use becomes more ubiquitous, their role in significant sleep loss could lead to long-term health consequences. For instance, chronic suppression of melatonin has been linked to increased risk of prostate, colorectal and breast cancers. And a persistent lack of sleep has been associated with obesity and diabetes. 
 
 "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," Czeisler said. "I think it's time to rethink that." 
 
 A poll released earlier this year by the National Sleep Foundation offered a glimpse at just how pervasive electronics have become in American bedrooms. Nearly 90 percent of adults and 75 percent of children reported having at least one electronic device in their bedrooms, and many reporting having multiple devices, such as televisions, laptops and tablets. 
 
 The sleep-disrupting effects of such devices might be even more significant for older teens, ages 15 to 17, almost all of whom reported having electronic devices in their bedrooms and were far more likely to use them at night than younger children, even when an early school morning loomed. ||||| Reading from electronic gadgets before going to bed can make it more difficult to fall asleep. Dr. Charles Czeisler discusses why this is with Tanya Rivero. Photo: iStock/Ximagination 
 
 Reading on electronic devices before bedtime can disrupt the body’s circadian clock, making it harder to fall asleep and become alert in the morning, according to a study from Brigham and Women’s Hospital in Boston. 
 
 Sleep researchers have long warned that watching TV, working on a computer and other activities involving artificial light in the evening can disrupt sleep patterns. But the type of short-wavelength enriched light, also...
– 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.)