Lots of teens are into vampires these days. Many more of them seem to be keeping vampire hours.

Take Alexa McGill, who has a very modern way of falling asleep. She does it while texting.

"Usually I'll wake up in the middle of night, reply to the text I fell asleep during, then stay up for a few more hours," said McGill, 16, who lives in Anoka. "Around 5 a.m. I'll try to get a couple more hours of sleep because I have to get up at 7 to get ready for work."

When Sam Humleker of Minneapolis was in 10th grade, he was almost always asleep by 9:30 p.m. Now, two years later, the 18-year-old is up till 1 a.m., texting, Skyping, checking his Gmail, digg.com and Facebook. He tells his mother, Cordelia Anderson, that 1 o'clock in the morning isn't so bad: "Some of my friends are up till 3 a.m.," he said.

Kind of makes the days when Mom or Dad would bust their little night owlets for shining a flashlight on a good book under the covers seem as quaint as a Norman Rockwell painting.

It's a problem that has gotten worse with each new technological temptation to come their way -- especially something as small and easy to slip under a pillow as a cell phone, which can be used for playing video games and Web browsing as well as texting. It's how teens socialize and it's available 24/7, making it hard to tear themselves away from just one more text, just a few more minutes on the Xbox.

The numbers tell the story. Half of adolescents get fewer than eight hours (they actually need nine or more) of sleep on school nights, and only 15 percent of them get adequate sleep, according to a new poll on teens and sleep from the National Sleep Foundation.

Problem behind the problem

All that wee-hours typing and surfing can produce more than fatigue. It's putting the teens' education, health and even safety at risk.

To parents -- many of whom think their teens are getting enough sleep when they're not -- the effects of sleep deprivations often appear to be something else.

"Often they bring their kids to me when they're having trouble in school, thinking they have issues with depression, drug use, or ADD, when actually not getting enough sleep is the problem behind the problem," said John Hoistad, an adolescent psychologist speaking as both a professional and the father of three teenage sons.

He noted the recent case of a boy who begins his junior year of high school this fall.

"He had a very high grade-point average, but lately his grades had been slipping," he said. "His parents brought him to see me, to figure out why. In his case, he was partly going away from what his parents, both self-made, high-performing people, wanted, and he was doing it by staying up all night, texting and going online."

Natural night owls

Teens are "not simply little adults" when it comes to sleep needs, said Dr. Michel Cramer Bornemann, co-director of the Minnesota Regional Sleep Disorders Center at Hennepin County Medical Center. "Adults require about eight hours of sleep each night, while teens need at least nine. Yet the average teen gets only about six. They're running in a chronic sleep-deprived state Monday through Friday."

Teens have a bit of what he calls a natural "sleep delay," or tendency to stay up later and sleep in later than their biological clocks will dictate when they reach maturity, a routine that doesn't jibe with school schedules.

Cramer Bornemann cautions against the "awareness gap" he sees in parents who think their teens are getting enough sleep.

"But Mom, I'm not even tired" is no assurance that's the case: When we're already sleepy, most of us are poor judges of our own need for sleep, he said, citing clinical studies. And that lack of awareness, coupled with the slower reactions and fuzzier thinking brought on by fatigue, can have dangerous consequences.

"Cognitive impairment behind the wheel of an automobile after one night of sleep deprivation is more severe than that of being legally intoxicated," Cramer Bornemann said. "All of these combinations make our adolescents a vulnerable population for which parents need to remain 'parent.'"

Sleep deprivation is also associated with obesity, because it decreases hormones that tell you that you feel full, and increases other hormones that make you feel hungry, he said.

Ann Hoxie, who supervises student health and wellness for St. Paul's public schools, says that tired students are more prone not only to short attention spans, but to mood swings and behavioral problems.

"I don't think parents are as aware of their older kids being tired as they could be," she said. "Even 15- and 16-year-olds still need parents to give them some structure."

Teen texting aficionado Alexa McGill figures she gets a total of about six -- interrupted-- hours of sleep a night.

"I know I do need that eight to 10 they say we do," she said. "I'm super tired a lot; it's getting to the point where I take naps during the day. When school starts I'll probably go to bed at 10 and just put my phone on silent."

Mom Helen McGill said that in the summer, she relaxes the rules, but that once school is in session, Alexa "has to turn her cell phone off after 8:30 p.m. on school nights. I may extend it to 9 this year."

We wish the McGills -- and the thousands of households negotiating the same sort of deal -- the best of luck in working that out.

Kristin Tillotson • 612-673-7046