THURSDAY, March 5 (HealthDay News) -- If you're over 50, and your friends have noted that you can't handle that third glass of wine as well as you used to, a new study confirms it's not their imagination.

Older adults who are social drinkers can become impaired by alcohol after only one or two drinks and not realize it, University of Kentucky researchers report.

Most studies on drinking are done with college students and involve binge drinking, but little attention has been paid to the effects of social drinking among older adults. As the population ages, there are more older drinkers. Yet little is known about age-related differences in the effects of alcohol, the researchers noted.

"Even though younger and older adults appear to have similar metabolism, the behavioral implications are different," said lead researcher Sara Jo Nixon, now a professor in the department of psychiatry, division of addiction medicine, and director of the Neurocognitive Laboratory at the University of Florida in Gainesville.

Small amounts of alcohol affect older adults more than younger adults, Nixon said. "Older adults thought they were fine when they weren't," she said. "You really can't rely on asking, 'Are you alright to drive,' even with lower amounts of alcohol. This may be particularly true for older adults."

The report was published in the March issue of the Journal of Studies on Alcohol and Drugs.

For the study, Nixon's group recruited 42 men and women aged 50 to 74 and 26 people aged 25 to 35. Participants were given alcohol or placebo to drink. Those given alcohol were given enough to reach the same blood alcohol level.

The researchers then had each person take a test called the Trail Making Test. In this exercise, people are asked to connect numbered and lettered dots as quickly as possible. The test evaluates visual-motor coordination, planning, and the ability to move from one thought to the next.

Each person took the test twice, first 25 minutes after drinking and then 75 minutes after drinking.