Being sleep-deprived slows our reaction time, said Dr. Michael Howell, a sleep expert with the University of Minnesota. That can mean hitting something we might otherwise avoid, like a child on a bicycle who suddenly veers off the sidewalk.
We're also more impulsive when we're tired, Howell said. It's like our brains revert to being teenagers. "We respond to things without thinking them through," he says. "... Road rage happens because people are sleep deprived."
The CDC report analyzed data from a 2009-2010 national behavioral telephone survey of more than 147,000 respondents. Approximately 4.2% of those surveyed reported having fallen asleep while driving at least once during the last month. That's one out of every 24 people.
That sounds like a small number, but the problem may be more prevalent over a longer period. A 2005 National Sleep Foundation poll found that 60% of drivers had driven while sleepy in the preceding year. In a 2010 national telephone survey, more than 40% of people admitted to having "fallen asleep or nodded off" while driving at some point in their lives, according to a report by the AAA Foundation for Traffic Safety.
Men were more likely than women to report falling asleep at the wheel, according to the new CDC report. Howell said men are more likely than women to have sleep disorders, especially sleep apnea. They're also less likely to regularly get enough sleep.
"We live in a sleep-deprived culture," he said. "There's a reason why there's a coffee shop on every corner. We don't sleep as much as we should."
Howell has five New Year's resolutions to ensure you're well rested in 2013. Check them out here.
(Jacque Wilson -- CNN.com Health writer/producer)