Description:This could give you nightmares: 1 in 24 U.S. adults say they recently fell asleep while driving.
And health officials think the number is probably higher. That's because some people don't realize it when they nod off for a second or two behind the wheel.
In a government study released Thursday, a little over 4 percent of U.S. adults said they fell asleep while driving at least once in the previous month.(0:33)