By Dennis Thompson
Heart disease remains a leading killer, said lead researcher Elizabeth Cespedes Feliciano. She's a staff scientist with the Kaiser Permanente Northern California Division of Research in Oakland, Calif.
"We really want our youth to be on a healthy trajectory," Feliciano said, "and it's a little alarming you would see adverse cardiometabolic profiles emerging even at an age as young as 13."
But it seems that very few kids are getting the kind of nightly slumber that would protect their future heart health.
Average sleep duration for kids in the study was only a little over seven hours per day, researchers found.
In fact, only 2.2 percent of the kids met or exceeded the average recommended sleep duration for their age group -- nine hours per day for kids 11 to 13 and eight hours per day for teens 14 to 17.
Further, nearly a third of kids slept less than seven hours.
"I was really struck by how little these adolescents are sleeping," said Dr. Andrew Varga, a sleep medicine specialist with the Icahn School of Medicine at Mount Sinai in New York City. "It's not totally surprising, given what I know about kids and their habits, but you would think there would be some drive for these kids to sleep more because they have a high sleep need."
Prior studies have shown that inadequate sleep boosts the odds for obesity. But Feliciano's team wanted to see whether a lack of sleep also affects other heart disease factors for kids.
So, they turned to 829 teenagers participating in Project Viva, a long-term study that recruited pregnant moms and has tracked them and their children for nearly 14 years.
At an average age of 13, the kids were asked to put on a wrist-worn movement sensor at bedtime that would track both their duration of sleep and whether they had restless sleep, Feliciano said.
The kids wore the sensors of seven to 10 days. They also underwent a series of screenings for heart health risk factors.
Teens with shorter sleep duration and more restless sleep wound up having the least healthy profiles. They had wider waist circumference, increased body fat, higher blood pressure, and lower levels of "good" HDL cholesterol.
Although cause-and-effect couldn't be shown in this stuidy, Feliciano believes the lack of good sleep did help trigger these risk factors, given prior research.
"We know from short-term experimental studies that when you deprive someone of sleep or interrupt their sleep, that has effects on some of the same cardiometabolic risk factors examined in this study," she said.
There are a number of ways sleep can affect heart health, Feliciano said.
Sleeplessness can spur changes in appetite, and also has been linked to decreased levels of physical activity. "You're awake longer, but you're often fatigued so you might not be engaging in sports or exercise," Feliciano said.
Sleep also is important in the regulation of blood pressure and blood sugar, Varga said.
"It's known that sleep is really helpful for lowering blood pressure," Varga said. "There are natural dips in blood pressure that occur throughout the night. When you're sleeping less, that happens less and offers less blood pressure control."
So what's keeping kids up at night?
Feliciano believes screen time is probably causing most of the sleep deprivation.
"Television viewing is still the dominant way these children are consuming media, but small screens are a concern as well, because you can bring those right into your bedroom," Feliciano said. "I do think screen media is a culprit for short and disrupted sleep, especially in this population that's very plugged in."
There's also a general lack of awareness among parents regarding the sleep needs of teenagers, Varga said.
"There's an impression that as kids become teenagers, we think of them as small adults who don't need as much sleep as younger children," Varga said. "That's totally not true. Even up to the early 20s, sleep needs are higher than that of a mature adult."
Parents need to put their foot down when it comes to screen time at bedtime, Feliciano said.
"I would recommend the bedroom be a screen-free zone," she said. "I think that would improve sleep duration and quality in adolescents."
The study was published June 15 in the journal Pediatrics.