For years researchers have debated the pros and cons of moderate alcohol drinking. No one suggests that alcoholism is healthy, but there has been evidence that having no more than one drink a day may actually bolster the heart or the brain, compared to drinking too much or not at all.
The connection between alcohol consumption and cognition -- the processes of thinking, learning and memory -- remains controversial.
"Studies have reported negative, positive and nonsignificant effects of alcohol consumption on cognition," say Dean Krahn, M.D., M.S., and colleagues from the University of Wisconsin. So Krahn decided to test whether the apparent differences in cognition in middle age corresponded more closely to drinking habits or to cognitive abilities in youth.
His findings are published in the July issue of the journal Alcoholism: Clinical and Experimental Research.
Ordinarily, it would be difficult to compare youthful and adult cognition in the same people without testing at both points in life. But Krahn's team was able to do exactly that by drawing on an ongoing database called the Wisconsin Longitudinal Study. The study has followed more than 10,000 men and women who graduated from Wisconsin high schools in 1957.
Helpfully, all the students completed a standard test of mental ability in their freshman and junior years of high school -- presumably before they did much drinking.
The Wisconsin Longitudinal Study surveyed these students again in 1964, 1975 and 1992. In 1992, the participants, then 53 years old, took another intelligence test and answered questions about drinking alcoholic beverages.
Krahn divided alcohol use into four categories: people who said they never drank; those who hadn't drunk in the last month; those who drank between one and 29 drinks in the previous month; and people who drank more than 30 drinks a month. The researchers analyzed the responses from men and women separately.
Looking only at the raw data (without considering high school cognitive abilities), men who consumed low levels of alcohol in 1992 had higher scores on the abstract reasoning test than those who drank either more or less. But when adjusted for earlier cognitive ability, the difference between non-drinkers and those who had one drink a day disappeared. (Test scores among men who had more than 30 drinks in the previous month remained lower than those who drank less.)
With the women, the simple view of the data indicated that both non-drinkers and heavy drinkers had lower scores at age 53 than moderate drinkers. But adjusting for adolescent cognitive ability wiped out those variations entirely.
"We observed no significant differences among the women between any level of alcohol use and cognition," Krahn says. In other words, any variation in cognitive ability was related to their teenage cognition rather than their middle-age drinking.
Other researchers have tried to make up for the lack of direct information on adolescent cognition by substituting the highest educational level reached by the participants. But analysis of the Wisconsin data shows that this may not always be accurate.
"Adjusting for educational attainment is not the same as adjusting for baseline cognitive ability," Krahn says, "even though it would make the analysis of the effects of long-term alcohol use on cognition much simpler if you could."
He noted the lack of significant differences may also be because the participants were still relatively young at age 53. He expects to see greater cognitive deficits as the group ages. Another round of interviews will go forward next year, when the grads are about 65, and may give more insight into the connection between alcohol use and cognition.
This research was supported by the Veterans Administration Merit Review Program and by the National Institute on Aging.
FOR MORE INFORMATION:
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By Aaron Levin, Staff Writer
Health Behavior News Service