Drinking alcohol, even in moderation, may be bad for the aging brain, according to new research.

The study, published in BMJ, found that moderate drinkers, compared to light drinkers and those who abstained from alcohol, were more likely to experience adverse brain function and a greater decline in mental skills.

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These findings contradict what some previous studies have concluded: drinking in moderation is beneficial. To better understand if moderate drinking is associated with changes in brain structure and function, scientists from the University of Oxford and University College London analyzed three decades of health data from more than 500 British civil servants who are part of the Whitehall II study (also known as the Stress and Health Study). The participants completed many cognitive tests and underwent MRI brain scans.

The researchers found that people who drank the most amounts of alcohol, none of whom were dependent on it, had the highest risk of hippocampal atrophy, which is an early marker of Alzheimer’s disease. Although it may not be a surprising find to see the damaging effect in those who drank heavily, the researchers also found that moderate drinkers were three times more likely to have hippocampal atrophy than those who didn’t drink.

“We were surprised that the light to moderate drinkers didn’t seem to have that protective effect,” study co-author Dr. Anya Topiwala told CNN. “These are people who are drinking at levels that many consider social drinkers, so they are not consuming a lot.”

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The study, conducted in the UK, supports the recent changes in the UK’s alcohol guideline recommendations, but it raises concern about the current limits recommended in the United States, the authors conclude in their paper. In the U.S., moderate alcohol consumption is considered up to 1 drink per day for women and up to 2 drinks per day for men, according to the U.S Department of Health and Human Services and U.S. Department of Agriculture.

But, it’s important to note that because this study is observational, there is no way to prove that moderate drinking causes dementia or brain decline.

"These types of studies also cannot account for all the (factors), and therefore they cannot, and should not, conclude causation," Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford, who was not involved in the research, told CNN. "Using all the available evidence provides a much more balanced approach for the public on deciding how much to drink."

Some of the factors the authors took into account were: age, sex, education, social class, physical and social activity, smoking, stroke risk and medical history. Despite this long list, there are many other factors the authors didn't look look at, which may have an effect on dementia, such as a person’s diet or their responses to chronic stress.

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