For people who are 55 or older, a single serving may hit them hard enough to make them a dangerous driver, reveal researchers.
Sara Jo Nixon, Ph.D., a professor in the departments of psychiatry and psychology at the University of Florida and doctoral candidate Alfredo Sklar tested how drinking legally non-intoxicating levels of alcohol affect the driving skills of two age groups: 36 people ages 25 to 35 and 36 people ages 55 to 70.
They found that although neither age group imbibed enough alcohol to put them over the legal driving limit, a blood alcohol level of 0.08, just one drink can affect the driving abilities of older drivers.
At the beginning of the study, both groups completed a driving task completely sober. The task took the drivers down a simulated winding 3-mile stretch of country road. The drivers stared straight ahead at a large computer monitor. Two computer monitors flanked the first, mimicking the side windows of a car and what the drivers would see in their peripheral vision.
A stereo system played driving sounds. A console included a steering wheel and brake and gas pedals. Occasionally, the drivers would encounter an oncoming car, but they did not encounter other distractions.
On a later day, the groups were further separated into groups. The first imbibed a placebo - a diet lemon-lime soda misted with a negligible amount of alcohol to mimic the experience of drinking alcohol.
A second group's drink was strong enough to produce a 0.04 percent breath alcohol level, and a third group's drink gave them a breath alcohol level of 0.065 percent - still below the federal legal level for drinking of 0.08.
But for the older drivers, they found, the small, legal levels of intoxication did affect their driving.
The study findings have been published in the journal Psychopharmacology.