Although people 50 or older in the study metabolized alcohol similar to how younger people did, they performed worse on special tests after having moderate amounts of alcohol and did not always realize when they were impaired. Soon after having alcohol, older adults also took on average five seconds longer to complete a test than their counterparts who did not have a drink.
"That doesn't sound like much, but five seconds is a big difference if you're in a car and need to apply the brakes," said lead author Sara Jo Nixon, Ph.D., a psychiatry professor at UF's McKnight Brain Institute. "It can mean the difference between a wreck, and not-a-wreck."
In 2007, an estimated 12,998 people were killed in crashes involving alcohol-impaired drivers, according to the National Highway Traffic Safety Administration.
"We still have a tremendous overhead in the United States of terrible tragedy with drinking and driving," said Edith Vioni Sullivan, Ph.D., a professor of psychiatry and behavioral sciences at the Stanford University School of Medicine. "We usually hear about the deaths; we seldom hear about the serious accidents that put people into nursing homes and hospitals for the rest of their lives."
More than half of adults older than 55 drink socially, according to a 2008 report from the Substance Abuse and Mental Health Services Administration. But few studies have focused on the short-term effects of social drinking among older adults. Previous research mainly investigated consumption of large amounts of alcohol at one time, and generally in young people. But results from studies of younger adults might not be applicable to older people because of age-related declines in cognitive skills, as well as changes in how alcohol is metabolized and removed from the body.
Nixon's group aimed to expand understanding of the effects over time of moderate levels of alcohol consumption in healthy, active older adults.
"You want to know how long does it take for them to become sober enough to engage in potentially dangerous activity such as driving," Sullivan said.
The study involved 68 nonsmokers — 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, 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 researchers 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.
"People shouldn't take it to mean that younger people can drink with impunity," Sullivan said.
During that same post-drinking phase, when the older adults were impaired, they didn't think they were. And in the second phase — an hour and 15 minutes after having alcohol — older adults thought their performance was impaired, even when it wasn't.
"An older person might say 'Really, I feel all right, I'm sure I can drive,'" Sullivan said. "But the study shows that you can't always take someone at their word."
So what advice would Nixon give to active, older adults?
"If you have a couple of drinks at dinner, sit around, have dessert — don't drive for a while."
The researchers didn't evaluate the role of interactions between alcohol and prescription and other medicines.
They hope to conduct studies with larger numbers of people, more age groups and a wider range of alcohol intake levels. Future studies in which subjects take multiple, more difficult tests; the same individual is observed under different circumstances; and differences between the sexes are evaluated might shed more light on alcohol effects in older active adults.
Czerne M. Reid | EurekAlert!
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