The report from a University of Florida research group in the Journal of Studies on Alcohol and Drugs involved 68 non-smokers – one group aged 50 to 74 and a comparison group aged 25 to 35 – who had at least one drink a month.

Within each group, some individuals were given alcohol while others were given a placebo beverage that did not elevate their breath alcohol levels. The groups were carefully matched by gender, body mass index, history of alcohol consumption and other demographic characteristics.

When a person consumes alcohol, concentration in the blood builds to a peak and then dissipates. During the first phase of the metabolic process, alcohol has a stimulating effect. During the second phase, there is a sedative or depressive effect.

During each phase – at 25 minutes and 75 minutes after alcohol consumption, respectively – participants were given tests that required them to draw lines connecting numbered and lettered dots on a paper, in chronological order, without lifting the pen from the paper. They were timed and evaluated for how many errors they made.

The first test involved numbers, while the second involved alternating between numbers and letters. Those tests give clues about a person’s mental processing related to movement, and about the ability to mentally shift from one problem-solving strategy to another.

The research team led by Sara Jo Nixon, PhD, a psychiatry professor at UF’s McKnight Brain Institute also asked participants to rate on 10-point scales how intoxicated they felt, and how much they thought the alcohol impaired their performance.

Older adults who had alcohol took longer to complete the tasks than younger adults who had alcohol. But there was no such age difference between the older and younger groups that had not had alcohol.

The researchers found that even though blood alcohol levels for participants in both groups rose at a similar rate right after drinking and reached the same peak, the older adults did worse on tests. That suggested the performance gap seen after moderate amounts of alcohol was not because of age-related differences in how the body processes the substance, but because of other factors influencing how alcohol affected the individuals.

In the test portion during the "stimulating" alcohol phase, older adults who had alcohol were slower than those who had not had any. In contrast, alcohol seemed to give the younger group a performance boost during that phase.