THURSDAY, Jan. 3, 2013 (HealthDay News) -- Driving drowsy is a major factor in traffic accidents and deaths in the United States, federal health officials reported Thursday.
Federal statistics state that 2.5 percent of fatal motor vehicle crashes and 2 percent of crashes with non-fatal injuries involve drowsy driving.
But, data gathering methods make it difficult to estimate the actual number of accidents that involve drowsy drivers. In fact, some studies have estimated that between 15 percent and 33 percent of fatal crashes may involve sleepy drivers. And deaths and injuries are more likely in motor vehicle crashes that involve drowsy driving, the report stated.
According to the report by the U.S. Centers for Disease Control and Prevention, more than 4 percent of drivers quizzed said they had driven while drowsy in the month before the survey.
"One out of 25 people reported falling asleep while driving in the past month," said CDC epidemiologist Anne Wheaton, the report's lead author. "If you think of how many cars you see every day, one out of 25 -- that's a pretty big number."
And those numbers may underestimate the scope of the problem, Wheaton said.
"These were people who realized they had fallen asleep while they were driving," she said. "If you fall asleep for even a moment you may not realize it -- so that's not even taking those people into account."
What's more, many people drive drowsy and don't fall asleep, but still pose a risk, Wheaton said.
"Driving while drowsy you are driving impaired. Your reaction time slows down, you're less attentive and it impairs your decision-making skills," she said. "So even if you don't fall asleep at the wheel, it's still a serious problem."
The report was published in the Jan. 4 issue of the CDC's Morbidity and Mortality Weekly Report.
In the study, researchers found that people who slept six hours or less were about twice as likely to report falling asleep while driving as those who got seven or more hours of sleep.
Other contributing factors include sleep disorders such as sleep apnea and insomnia, Wheaton said.
In 2009, approximately 30,000 people were involved in car crashes due to drowsy driving and 730 died, according to the U.S. National Highway Traffic Safety Administration.
Drowsy driving also varied state-to-state, from a low of 2.5 percent in Oregon to a high of 6.1 percent in Texas, the report found.
The findings were based on a survey of almost 150,000 drivers.
The best way to prevent drowsy driving is to get at least seven hours of sleep. And people with a sleep disorder should seek treatment, the CDC said.
The agency also recommends not drinking alcohol or taking sedatives before sliding into the driver's seat.
Wheaton said some of the signs of drowsy driving include: not remembering the last couple of miles driven; missing an exit on a highway; having trouble staying in a driving lane; and struggling to keep your eyes open.
"If you have these symptoms you need to get off the road and rest until you're not sleepy anymore," she said. "Even better is to change drivers with someone who is not sleepy."
Russ Rader, a spokesman for the Insurance Institute for Highway Safety, said: "Drowsy driving is a lot like distracted driving -- it's not something you can outlaw and solve the problem. Technology may help. High-tech, crash-avoidance systems can alert drivers to hazards or even take action autonomously if your attention wanders or you're sleepy and may prevent a lot of crashes in the future. These systems are always on alert and never get tired like people do."
For more on driving while drowsy visit the AAA Foundation for Traffic Safety.