Consumption of large amounts of alcohol over a long period of time may shrink the brain, researchers say.

Excessive drinking appears to accelerate the natural reduction in brain size caused by ageing, according to brain scans of more than 1,800 people. The more people drank, regularly, the more that the ratio of brain volume to skull size fell, especially among older women.

The heaviest drinkers had brains that were up to 1.6 per cent smaller than non-drinkers, although the researchers have not yet correlated this with performance in mental tests. The findings, yet to be published, have been presented to the American Academy of Neurology conference in Boston.

Volunteers were classified as non-drinkers, former drinkers, low drinkers (one to seven drinks per week), moderate drinkers (eight to fourteen drinks) or high drinkers (more than fourteen). Brain volume decreased 0.25 per cent on average for every jump in drinking category. There is a natural reduction of about 0.19 per cent every year due to ageing, researchers said. Women were found to have a reduction of up to 0.29 per cent for every jump in category; for men it was 0.2 per cent.

The volunteers had an average age of 60, with a brain-to-skull ratio of under 80 per cent of what it was when they were young adults. Previous studies have suggested that alcohol-dependent people have smaller brain volumes than others. It is believed that this is due to ethanol, which causes an alcoholic’s brain to shrink with ageing to a greater extent.

Carol Ann Paul, a postgraduate researcher from Wellesley College in Massachusetts, who conducted the study, said yesterday: “Research has shown that there is a beneficial effect of alcohol in reducing incidence of cardiovascular disease in people who consume low to moderate amounts of alcohol.

“However, this study found that greater alcohol consumption was negatively correlated with brain volume. It is only a snapshot, but women in their seventies appear to be the most affected by large amounts.”

People with a 12-year history of heavy drinking had smaller brains than those who had begun drinking heavily more recently, she said, adding: “There is a battery of mental tests that we can look at to see if high levels of reported drinking have an impact on people’s performance.”

Jeffrey Bird, of the Institute of Cognitive Neuroscience at University College London, said that the relation between brain size and intelligence was complicated. “It is widely acknowledged that alcohol can damage areas of the brain associated with memory and learning, but the first 25 years of life are the most important in terms of brain growth, after which it naturally shrinks in size. A bigger brain doesn’t necessarily mean a better brain,” he said.

A spokesman for the charity Alcohol Concern said: “This study adds to what we already know, which is that alcohol misuse and dependency can lead to generalised brain damage and neurological disorders.”

Average household spending on alcohol has risen 21 per cent in Britain in the past five years, according to the charity.

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