MONDAY, May 20 (HealthDay News) -- Young drivers who get behind the wheel while drowsy run a higher risk of getting into car crashes, but Australian researchers have found that not catching up on missed sleep on weekends puts them in even greater danger of having an accident at night.

"This is another challenge to adolescents that comes with lack of sleep," said Dr. Flaura Winston, co-scientific director and founder of the Center for Injury Research and Prevention at Children's Hospital of Philadelphia.

"You have to be ready, body and mind, to drive," she said. "If you are exhausted, you are neither ready body nor mind."

In tackling this challenge, both parents and the community have roles to play, said Winston, who was not involved with the study.

"This is a safety concern," she said. "If the teen doesn't get enough sleep, then they are at increased risk for crashes, so parents need to step in."

Parents should see their role as one that helps their teenager stay safe without being controlling, Winston explained. They can encourage their children to get more sleep, and provide rides at night to ensure that their teens are not driving exhausted.

One of the more positive things parents can do is let their teen sleep late on the weekends, Winston noted. "Teens need their catch-up sleep," she said. "They do need to sleep late on the weekends."

There are also social factors that limit teens' sleep. For example, many high schools start classes very early, cutting into students' sleep time, Winston pointed out. "Studies have shown that later school start times are better for adolescents," she said.

Not only do they start school early, but "they have long days. They have sports, after-school activities and studying, so there are things that are way beyond the family that put these teens at risk when it comes to driving," Winston said.

The report was published online May 20 in the journal JAMA Pediatrics.

To look at what role sleep plays in teen car crashes, a team led by Alexandra Martiniuk, an associate professor at the George Institute for Global Health in Sydney, collected data on more than 20,000 drivers aged 17 to 24.

The investigators found that those who said they slept six or fewer hours a night had a 21 percent higher risk of having a car accident than those who got more than six hours of sleep.

Moreover, those who got less sleep on the weekends had a 55 percent increased chance of having a single-car accident, where the car drifts or swerves off the road, they added.

Most accidents (86 percent) happened between 8 p.m. and 6 a.m., the researchers noted.

"Sleeping six hours a night is enough to put young drivers at significant risk of having a car crash. With work, study and social commitments, especially on weekends, it is easy to miss out on the extra hours of sleep we need," Martiniuk said in a statement.

More than 3,000 people die every day in car crashes around the world -- that's more than 1.3 million car-related deaths a year, with between 20 million and 50 million people injured or disabled, the researchers noted.

In the United States alone, it is estimated that 20 percent of all car crashes are the result of drowsy driving, which adds up to 1 million crashes, 50,000 injuries and 8,000 deaths a year, the study found.

More information

For more on teen driving, visit the Children's Hospital of Philadelphia.