WASHINGTON (AP) -- To wake parents up to the importance of snoozing, sleep experts warned Tuesday that seemingly energetic children who dodge bedtime for other activities are more prone to injury, poor school performance and crankiness.

"A tired child is an accident waiting to happen," said Dr. Carl Hunt, director of the National Center on Sleep Disorders Research at the National Institutes of Health.

Many children with chronic sleep deprivation may not seem tired and may even appear to be overactive.

Hunt said injuries on bicycles and on playground equipment are more likely to occur when a child is sleep-deprived, and if poor sleeping habits continue as kids grow older, "the stakes get higher."

"It turns into the teenager who is drowsy and driving a car," he said.

Research shows that bad sleep habits for children can carry over into poor health for adults -- causing heart ailments, respiratory problems and obesity, said Dr. Claude Lenfant, director of NIH's National Heart, Lung and Blood Institute.

Children ages 7 to 11 require at least nine hours of sleep each night on a regular basis to do their best in school and extracurricular activities, NIH said.

Inadequate sleep results in difficulties with focused attention, irritability, easy frustration and difficulty controlling emotions.

NIH estimates that more than 70 million Americans of every age are sleep-deprived.

"Unfortunately in this 24-7 society we're living in these days, it creates many distractions and obstacles to getting a good night's sleep," said Hunt. "We're living in a society that doesn't value sleep enough."

Besides increased extracurricular activities and homework, things that are getting in the way of a good night's sleep for a child are television, the Internet, cell phones and e-mail -- with many of those distractions located in children's bedrooms.

"These give children lots of opportunity to do other things besides sleep," Hunt said.

To address health problems associated with sleep deprivation, NIH launched its Star Sleeper educational campaign to raise family awareness to the problem.

On Tuesday, it announced three winners of its "How I Get a Heap of Sleep" contest in which children described their tactics for getting nine hours of sleep each night. One winner was Danielle Wodka, 7, of Lemont, Ill. Her sleep strategies included taking a warm bath and saying her prayers.

Other winners -- including Amanda Davol of Somerset, Mass., and Qian Wang of Fort Thomas, Ky. -- said they listened to soothing music or read a book to lull them into sleep.

Getting children in the mood for bedtime is half the battle, says Danielle's mother, Chris Wodka, of Lemont, Ill.

"It's a struggle with Game Boy and the TV shows," said Wodka