Ponder this moms and dads: If you knew that children who use their smart phone when they should be sleeping are hurting their immune system, reducing their ability to perform academically, and increasing behavior problems and the risk for weight gain, would you let them have the device at night?

Those are the risks children face when at bedtime they have unlimited access to smart phones, iPads, and similar devices, according to University of California researcher Jennifer Falbe, the lead author of a study about the impact of this technology on sleep deprivation. The results — coming from a study of more than 2,000 youngsters in the fourth and seventh grades in Massachusetts — were published recently in the journal Pediatrics.

“The findings caution against unrestricted access to media in children’s bedrooms,” Ms. Falbe said.

Michael Neeb, administrative director for Mercy Sleep Services in Toledo, agrees.

“This is a fairly well-known phenomenon, and there are multiple reasons why this is a problem,” said Mr. Neeb, who added that texts and other alerts “coming through in the middle of the night” interrupt sleep.

“Much of what children do on smart phones is highly stimulating ... from video games to the emotional content of a text,” he added. “At a basic level, it’s the amount of time being spent on the smart phone that’s eating into the amount of time that should be allocated for sleep.”

Mr. Neeb said the phones chip away at about 20 minutes of a person’s sleep every night. Though that may not seem like a lot, there’s more to it: the light that shines directly into a user’s eyes is extremely intense, he said.

“The light shuts off the brain production of melatonin, a hormone within our bodies that help us fall asleep and stay asleep,” he said. “All these factors converge to create a loss of sleep time or an impairment of quality of sleep.”

Mercy Children’s Hospital urges parents to shut off these popular devices about 30 minutes before bedtime. The hospital recommends nine to 10 hours of sleep time every night for teens, 10 to 11 hours for school-age youngsters, 11 to 13 hours for preschoolers, 12 to 14 hours for toddlers, and 14 to 15 hours for infants.

Parents constantly wrestle with the issue of getting smart phones from their adolescents and teenagers at night, and according to Tina Mayhugh, mother of daughters ages 20, 17, and 15, the battle is going to go on for “years to come.”

“A lot of parents are having a tough time with their kids taking their phones to bed,” said Ms. Mayhugh, a registered sleep technician at Mercy St. Ann Sleep Disorder Center. “Kids are obsessed with them. They use them as alarm clocks, and when kids can’t sleep or don’t want to go to bed, they start reaching out to those who reach out to them.”

Her daughters don’t have smart phones, but own other technology such as iPods, iPads, and tablets that let them connect to the web. Ms. Mayhugh describes one daughter as always on those electronic tools, watching YouTube and losing track of how long she has been on them.

“And I think that’s the case for a lot of people: they get lost in there and don’t realize what time has passed,” said this mother who has employed various triggers to remind her girls when it’s time to shut down the devices and prepare for bed. A timer on the family router that shuts down access to Wi-Fi does the trick.

“A lot of routers have parental controls on them,” she said. Hers is turned off overnight and turned on at 6 a.m.

Mr. Neeb said students have described their phones as their link to the outside world.

They have asked him, “‘do you unplug your land line at night?’ ” he said, adding that silencing ring tones and putting the devices in another room are options.

“You need contact with the outside world, but things like iPads can be kept out of the bedroom,” he said.

The Mercy sleep services director said this is a grave issue that must not be taken lightly.

“The research suggests that not getting enough sleep at night for kids affects their ability to perform well in school … which then leads to long-term consequences in a child’s life,” he said.

“When we don’t sleep well or long enough, we have immediate, next-day consequences of poor concentration and attention, qualities that are needed in the classroom setting. There are numerous research studies that say when kids get enough sleep, their grades improve, and when not, we see problems in their academic performance and grades.”

What about the glow of television screens? Mr. Neeb said they also can be problematic, but said light from a TV is not directly in a viewer’s eyes.

“So you don’t have all the serious problems you have with small-screen devices,” he said. He pointed out that “People have been going to bed with televisions on for decades, but [using a small-screen device at night] is a new problem, and an increasing one.”

Like children, many adults want to stay connected until the wee hours, but he said they tend to have a better handle on behavior control. Children are still learning to manage the crabbiness and irritability that results from a lack of sleep.

“Bedrooms should be for sleep, not for social communication, game playing,” he said. “The whole psychology of the bedroom should be for sleep.”

Contact Rose Russell at: rrussell@theblade.com or 419-724-6178.

First Published January 25, 2015, 5:00 a.m.