Once upon a time, the warm glow coming from a child's bedroom after lights out meant a book and a flashlight were in use. Today, chances are good that the light is more a shade of eerie white -- and it's coming from a smartphone, tablet or laptop.
Chances are good, too, that it's interfering with their sleep in a different way than a favorite Harry Potter novel ever did.
New research indicates that achieving more and higher quality zzzz's for all ages may come down to finding optimal ways of shutting our i's -- our iPads and iPhones, that is, along with our Kindles, video games and laptops. Even extremely brief flashes of bright light -- we're talking two milliseconds -- at night not only enhance our alertness, but shift our circadian rhythm and alter our hormones, according to a 2011 study led by Jamie Zeitzer, assistant professor of psychiatry and behavioral sciences at Stanford School of Medicine.
"It's very well-proven: Bright screens at night can shift your circadian rhythm by hours," says Dr. Emmanuel J. Mignot, a physician and a professor of sleep medicine at Stanford School of Medicine. "Physiologically, it makes sense. We're not that different than animals. We synchronize our circadian rhythm to light, and light has a profound effect."
Reading a paper book, with light reflecting off the page, does not have the same effect.
"The screen of your phone shifts your circadian rhythm much, much more," Mignot says. "It's very dangerous. It tells (your brain) abnormally that the sun is still up. The effect is stronger with electronics, because it flickers; it's more stimulating to the brain.
"In the middle of the night, just a tiny amount of light -- so brief it doesn't even wake you up, just opening your computer (or glancing at your phone) -- can shift your clock by hours. It can make an early bird into a night owl."
Tough on teens
It's all the harder on adolescents, whose changing circadian rhythm already makes it tougher to fall asleep until later at night -- just at the time physiological changes mean they require as much sleep as young children.
"And fragmenting your sleep," Mignot says, "impacts learning."
Parents have been largely left to their own devices, so to speak, in determining healthy electronics use for kids.
Madelaine Cunningham, of Clayton, mother of two teens, caught on two years ago when she discovered a direct link between late-night texting by her 17-year-old son and "grades suffering."
So she and her husband instituted a ritual where they take a basket around and collect cellphones, laptops, even the TV and game controllers, an hour before they go to bed.
Dr. Melissa Lim, medical director of the Redwood Sleep Center in Redwood City, says it's especially important to avoid interactive use, such as texting, gaming or searching the Internet, which can lengthen the normal time -- usually 10 to 20 minutes -- it takes to fall asleep. Contentious interaction, she adds, can lengthen it more.
Still, she thinks there's some room for discretion.
"We say 'turn off all technology a few hours before bedtime,' " Lim says. "But you want to ask 'Is it harmful?' Technology that is passive -- such as a relaxing TV program or music -- can distract you from your daily problems, which helps set up sleep."
She recommends content with no dialogue -- movies like "Winged Migration," Andy Goldsworthy videos or nature shows on Animal Planet.
"All of us find it difficult to wind down if we are also engaging with others," says Allison Harvey, a professor of psychology and director of the Golden Bear Sleep and Mood Research Clinic at UC Berkeley, but, she adds, "some interactions can cause stress," including interpersonal conflicts and pressure from friends to stay up late to text or instant message.
Interactive electronics use is most prevalent among adolescents and teens, polls show. Add to this getting up early on school days and sleeping in on weekends, and "most teenagers have a sleep schedule that ends up feeling as though they've flown from San Francisco to New York every week," Harvey writes in an email.
How we wake up -- be it to Pandora or an old-fashioned alarm clock -- matters less, Lim says, than having a regular wake-up time, adding that you should avoid using a cellphone for an alarm clock if you can't resist texts, calls and emails all night.
Harvey's opinion is more clear cut.
"Keep illuminated devices out of your bedroom," she says. "Charge devices in the kitchen. ... Laptops, tablets and TVs do not get to sleep in the bedroom with you."
The question is, how?
Betsy Ortiz, Walnut Creek mother of two, says she sometimes feels she has to carry the iPad and phones around the house with her.
"The minute I evict the kids from one screen, they're on another," Ortiz says.
Complicating the issue is that many schools mandate homework be done online.
"I treat a lot of kids who have only six hours to sleep a night, and are anxious when they get into bed," Lim says. To avoid late-evening electronics-induced stress for her own son, now 18, she and her husband set a deadline when he had to have his homework done. To make it stick, they installed a timer to shut off their modem at the allotted hour.
"It was really painful for everyone, at first," she laughs. "But it works. He had to budget his time."
To limit kids' time on electronics overall, students also need to distinguish between playtime and schoolwork, Lim says. She suggests software that blocks social media during schoolwork.
Keep them busy
She also recommends scheduling some, but not too many, activities for kids, in order to leave less time for gaming and social media. If the activity involves exercise, all the better for sleep, she says.
Ortiz thinks limiting kids' overall time on electronics is worth the effort. Their family's rule? No TV, video or computer games Monday through Thursday and just an hour and a half daily Friday to Sunday.
"I know I'm very controlling, but I think it's important to place limits," Ortiz says. "I see lots of parents with no real boundaries who want to be sure that their kid isn't left out because he or she doesn't have the latest, greatest iTouch. ... Both of my kids are voracious readers, and I chalk that up at least in part to (our rules about) computer time."
Cunningham is of the same mindset. She notes that with electronics safely stowed at night, her 13-year-old son likes to spend about 20 minutes reading a book in bed. "And," she says, "he falls asleep quickly."
DeAnne Musolf writes for www.catapultbrainscience. com.