PARIS • Even moderate drinking could lead to brain damage and a slight decline in mental skills, according to a study released yesterday that calls into question many national alcohol guidelines.
Men and women who have 14 to 21 drinks a week over decades are two to three times more likely than non-drinkers to show atrophy in the hippocampus, a part of the brain that governs memory and the ability to keep one's bearings, said the study, published in the medical journal BMJ.
They also performed more poorly on a specific verbal test, though other language functions appeared to remain unchanged.
A single drink was defined as containing 10 millilitres of pure alcohol - the equivalent of a large glass of wine, a pint of 5 per cent beer, or a shot of spirits like whisky or vodka.
Last year, the British government revised its guidelines for alcohol consumption, lowering the recommended maximum for men and women to 14 "units", or drinks, spread out over a week.
In other countries, that threshold is set higher for men: 35 units in Spain, 24.5 in the US, 21 in Denmark and Ireland, and 19 in New Zealand. But for women, the guideline for maximum weekly consumption in all of these nations, except for Spain, is 14 drinks at most.
The negative impact of heavy drinking on the brain is well documented, but research on potential damage from "moderate" consumption - up to now defined as two or three drinks a day, on average - has been scant and inconclusive.
To probe further, researchers at the University of Oxford and University College London combed through data on 550 men and women monitored during 30 years as part of an earlier study.
Volunteers reported periodically on their drinking habits, and scientists carried out brain tests at regular intervals. None were alcoholics at the outset.
The effect of 14 to 21 units of alcohol on the hippocampus was clearly shown by imaging technology.
Mental performance tests were less conclusive: only one measuring language fluency showed a clear impact, while others showed no decline in brain function.
"Alcohol consumption - even at moderate levels - is associated with adverse brain outcomes," the researchers concluded.
The findings "support the recent reduction in alcohol guidance in the United Kingdom, and question the current limits recommended in the United States", they wrote.
Because the new study was observational, no firm conclusions could be drawn about cause and effect. Also, the sample size was small.