MONDAY, June 10, 2013 (HealthDay News) -- Having a designated driver sounds like a great idea, but a new study found that more than one-third of those who were supposed to drive their pals home safely had been boozing it up themselves.
And some were legally drunk.
The study has limitations that prevent it from being definitive, and researchers aren't sure how much danger lurks in designated drivers who have a drink or two. But the message is clear, said study author Adam Barry, an assistant professor at the University of Florida: Some designated drivers are drinking when they should be abstaining.
"While more of the designated drivers didn't drink than did drink, which is a good thing, you have people being selected because they're the least drunk, or the least intoxicated or they've driven drunk before," Barry said. "The only real safe option is to completely abstain."
The researchers, all from the University of Florida, Gainesville, went to an unidentified college-area town and talked to almost 1,100 bar patrons, mostly white, male and college-aged. They then gave blood alcohol tests to 165 people who said they were serving as designated drivers -- those who are expected to take care of driving their friends home so the others can drink.
Sixty-five percent, or 108, of the designated drivers had zero alcohol in their systems. Another 17 percent, or 28, had a blood alcohol level of between 0.02 and 0.049 (grams of alcohol per 210 liters of breath). And 18 percent, or 29, were at 0.05 or more; the legal limit is 0.08 or higher.
It's not clear how many of the designated drivers actually drove after taking the blood alcohol tests, nor do researchers know if they were able to sober up before driving.
The researchers also didn't examine how many of the designated drivers were legally drunk at 0.08 or higher. Barry said the researchers chose to look at those above 0.05 because experts think drivers are significantly impaired at that level; some public health advocates want to lower the legal level for driving to 0.05.
People can be arrested for driving while intoxicated at levels under 0.08, but they must show signs that they're impaired.
Why does it matter if designated drivers have had only a bit of alcohol? Barry said they may have more trouble handling the task of driving with boozed-up passengers: "You've got roughhousing, unruly passengers, music -- so many competing factors on top of your ability to process information and brake and steer effectively," he explained.
Is it realistic to expect designated drivers to not drink at all? James Lange, an alcohol researcher and coordinator of Alcohol and Other Drug Initiatives at San Diego State University, said it is.
Because people's alcohol tolerance varies, "it would be difficult for me to make a blanket statement that a certain amount is OK," Lange said. "The easiest recommendation is that they don't drink at all."
E. Scott Geller, a professor who studies alcohol use at Virginia Tech, suggested that "we should not trust a designated driver to be sober." Instead, he said, there should be ways to guarantee that they don't drink, such as providing rewards at a party or bar if blood alcohol tests shows they've abstained.
The study appears in the July issue of the Journal of Studies on Alcohol and Drugs.
For more about alcohol abuse, try the U.S. National Library of Medicine.