Alcohol consumption, even in moderation, is linked to a greater risk of adverse brain outcomes and a more severe decline in cognition, according to a new U.K. study published in the journal The BMJ.
While heavy drinking is known to correlate with poor brain health, few studies have looked at the impact of moderate drinking on the brain; and for those that have, the results are inconsistent.
So a research team from the University of Oxford and University College London set out to investigate whether moderate alcohol consumption has a beneficial or harmful association — or no association at all — with brain structure and function.
They analyzed data from the Whitehall II study which measured the weekly alcohol intake of 550 healthy men and women (average age 43) over a 30 year period (1985-2015). None of the participants were alcohol-dependent. Brain function tests were carried out at regular intervals and at the end of the study (2012-15), participants underwent an MRI brain scan.
After adjusting for factors such as age, sex, education, social class, physical and social activity, smoking and stroke risk, the researchers found that higher alcohol consumption over the 30-year study period was associated with increased risk of hippocampal atrophy, a form of brain damage that affects memory and spatial navigation.
A unit of alcohol is a UK term that represents 10 milliliters (ml) of pure alcohol. This equals about a half a pint of average-strength (four percent) lager.
In the study, people who consumed more than 30 units a week were at the highest risk compared with abstainers. But even those drinking moderately (14-21 units per week) were three times more likely to have hippocampal atrophy compared with abstainers. There was no protective effect of light drinking (up to seven units per week) over abstinence.
Higher consumption was also associated with poorer white matter integrity (critical for efficient cognitive functioning) and faster decline in language fluency. No association was found, however, with semantic fluency or word recall.
The researchers assert that this is an observational study, so no firm conclusions can be drawn about cause and effect and that some limitations could have introduced bias. As such, they say their findings have important potential public health implications for a large sector of the population.
“Our findings support the recent reduction in U.K. safe limits and call into question the current U.S. guidelines, which suggest that up to 24.5 units a week is safe for men, as we found increased odds of hippocampal atrophy at just 14-21 units a week, and we found no support for a protective effect of light consumption on brain structure,” they write.
“Alcohol might represent a modifiable risk factor for cognitive impairment, and primary prevention interventions targeted to later life could be too late,” they concluded.