By Stephanie Stahl

PHILADELPHIA (CBS) – New research shows just one drink can be one too many for certain drivers.

It seems innocent enough. Doctors say that, for most people, one drink won’t get them legally drunk.

But new research has found that for people over 55, one drink can turn them into dangerous drivers.

“They would both speed up and slow down,” says Professor Sara Jo Nixon, of the University of Florida, who led the research that compared moderate drinking in two age groups: people between 25 and 35 and those between 55 and 70 years old.

They were tested inside a driving simulator; first, sober to find a baseline, then after one drink.

Their blood-alcohol level was kept below the legal limit for intoxication, so no one in the study was ever legally “drunk.”

For the younger group, one drink didn’t affect or change driving abilities.

But the study found a significant impairment after just one drink in the old group.

“These were really moderate doses of alcohol, and to find these kinds of effects at that level was somewhat surprising to us,” Nixon says.

It’s unclear what caused the driving impairment. The research accounted for variables like weight and metabolism, and they couldn’t find any significant differences, or indications of why one drink would have such an effect on the older age group.

“The short answer is, we don’t really know,” Nixon says.

Prof. Nixon thinks the research shows there’s a need to re-evaluate blood-alcohol levels and what’s considered safe for driving.

For more information on the study, click here.

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