Washington: When a person's mental abilities as a teenager are factored in, most of the reported health benefits of moderate drinking on brain functioning in middle age become moot, suggests a new study.

"Studies have reported negative, positive and non-significant effects of alcohol consumption on cognition," say Dean Krahn 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, says a report in 'Health Behaviour'.

Published in the July issue of the journal 'Alcoholism: Clinical and Experimental Research', the study has followed more than 10,000 men and women who graduated from Wisconsin high schools in 1957. Krahn's team drew on an ongoing database called the Wisconsin Longitudinal Study. The 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 analysed 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. 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.

"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.

According to the report, 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."

ANI