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 released Thursday, a little over 4 percent of U.S. adults said they fell asleep while driving at least once in the previous month. Some earlier studies reached a similar conclusion, but the survey by the was far larger.

The study found was more common in men and in people ages 25 to 34.

The results are from a survey of 147,000 adults in 2009 and 2010.

More information: CDC report: www.cdc.gov/mmwr