This could give you nightmares: 1 in 24 U.S. adults say they recently fell asleep while driving. And health officials behind the study 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. "If I'm on the road, I'd be a little worried about the other drivers," said the study's lead author, Anne Wheaton of the Centers for Disease Control and Prevention. In the CDC study released Thursday, about 4 percent of U.S. adults said they nodded off or fell asleep at least once while driving in the previous month. Some earlier studies reached a similar conclusion, but the CDC telephone…