A one-hour delay of school starting time in a large school district in Kentucky is giving teens a better night's sleep and helping them remain more alert in the classroom.  But it may also be saving their lives: The later school start times are associated with fewer car crashes among 17- and 18-year-old drivers, according to a study published in the Journal of Clinical Sleep Medicine

Crash rates dropped 16 percent in the county that changed the high school start times one hour later and increased about 8 percent in the rest of the state during the same period of time.

Fred Danner is chairman of the Department of Education and Counseling Psychology at the University of Kentucky and lead author of the study.  He says the work did not control for risky behavior like cell phone use or alcohol consumption while driving.  But he says the findings are consistent with what already has been reported about the harmful effects of even mild sleep deprivation on daytime alertness.

"A lot of the things we consider typical adolescent behavior - mood swings, lack of focus, spacey, clumsy - those are exactly the same symptoms that we find in sleep labs of sleep deprivation," he says.

Danner says a shift underway in many school districts toward earlier school start times for teens comes at time when the adolescent sleep cycle is pushing the body clock an hour later at night. 

"And the school start times is pulling them out of bed an hour earlier. That is two hours every single night. By the end of the week, they build up a devastating sleep debt."

Danner doesn't expect high schools across the country to immediately adopt later classroom start times. But the move does address the issue of teen sleep and health, which he says must be taken more seriously.