Drinking even moderate amounts of alcohol can damage the brain and impair cognitive function over time, researchers have claimed.
While heavy drinking has previously been linked to memory problems and dementia, previous studies have suggested low levels of drinking could help protect the brain. But the new study pushes back against the notion of such benefits.
“We knew that drinking heavily for long periods of time was bad for brain health, but we didn’t know at these levels,” said Anya Topiwala, a clinical lecturer in old age psychiatry at the University of Oxford and co-author of the research.
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Writing in the British Medical Journal, researchers from the University of Oxford and University College London, describe how they followed the alcohol intake and cognitive performance of 550 men and women over 30 years from 1985. At the end of the study the team took MRI scans of the participants’ brains.
None of the participants were deemed to have an alcohol dependence, but levels of drinking varied. After excluding 23 participants due to gaps in data or other issues, the team looked at participants’ alcohol intake as well as their performance on various cognitive tasks, as measured at six points over the 30 year period.
The team also looked at the structure of the participants’ brains, as shown by the MRI scan, including the structure of the white matter and the state of the hippocampus – a seahorse-shaped area of the brain associated with memory.
After taking into account a host of other factors including age, sex, social activity and education, the team found that those who reported higher levels of drinking were more often found to have a shrunken hippocampus, with the effect greater for the right side of the brain.
While 35% of those who didn’t drink were found to have shrinkage on the right side of the hippocampus, the figure was 65% for those who drank on average between 14 and 21 units a week, and 77% for those who drank 30 or more units a week.
The structure of white matter was also linked to how much individuals drank. “The big fibre tracts in the brain are cabled like electrical wire and the insulation, if you like, on those wires was of a poorer quality in people who were drinking more,” said Topiwala.
In addition, those who drank more were found to fare worse on a test of lexical fluency. “[That] is where you ask somebody to name as many words as they can within a minute beginning with a certain letter,” said Topiwala. People who drank between seven and 14 units a week were found to have 14% greater reduction in their performance on the task over 30 years, compared to those who drank just one or fewer units a week.
By contrast, no effects were found for other tasks such as word recall or those in which participants were asked to come up with words in a particular category, such as ‘animals.’
Expert reaction to the the study was mixed. While Elizabeth Coulthard, consultant senior lecturer in dementia neurology at the University of Bristol, described the research as robust, she cautioned that as the study was observational, it does not prove that alcohol was causing the damage to the brain.
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In addition, the majority of the study’s participants were men, while reports of alcohol consumption are often inaccurate with people underestimating how much they drink – an effect that could have exaggerated the apparent impact of moderate amounts of alcohol.
Dr Doug Brown, director of research and development at Alzheimer’s Society said that the new research did not imply that individuals should necessarily turn teetotal, instead stressing that it was important to stick to recommended guidelines.
In 2016, the Department of Health introduced new alcohol guidelines in the UK, recommending that both men and women drink no more than 14 units of alcohol each week – the equivalent of about six pints of beer or seven 175ml glasses of wine.
“Although this research gives useful insight into the long-term effects that drinking alcohol may have on the brain, it does not show that moderate alcohol intake causes cognitive decline. However, the findings do contradict a common belief that a glass of red wine or champagne a day can protect against damage to the brain,” said Brown.