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Moderate Drinking Associated With Harm to the Brain

 Uh-oh... looks like any benefits of moderate alcohol consumption may not extend to the brain, at least in men. A  recent study found that moderate alcohol consumption over the course of a 30 years was associated with increased odds of hippocampal atrophy (brain damage in the hippocampus of the brain) - when compared to abstainers. Hippocampal atrophy causes memory problems and affects spatial navigation, and is also an early characteristic of Alzheimer's disease and other dementias. This result occurred in a dose dependent fashion - meaning the more that was drunk regularly, the more the atrophy in that area of the brain.

The heavier drinkers (when compared to abstainers) also had a faster decline in verbal skills ('verbal fluency") and changes in the white matter of the brain (specifically "corpus callosum microstructure"). There was no protective effect of light drinking when compared to abstainers (the 2 groups had similar results). **However, the researchers also reported: "The hippocampal atrophy associations we found in the total sample were replicated in men alone but not in women." Note: there were few women in the study (only 103 out of 527 studied) and even fewer were "heavy" drinkers (14 women), but one wonders - why not? Why didn't women drinkers have these brain changes?**

So how much did the moderate drinkers drink? They really didn't drink that much, but there were different groups: the abstainers (less than 1 unit of alcohol a week), “light” drinking was between 1 and <7 units, “moderate” drinking as 7 to <14 units a week for women and 7 to <21 units for men, and the heavier drinkers - those that drank more units per week, for an average of 30 units a week. What is a "unit" of alcohol? A medium glass of wine has about two units of alcohol, and so does a pint of  ordinary strength beer or lager. Thus the male moderate drinkers drank about a medium glass of wine or a beer each night, and maybe a little extra on the weekends. (In other words, not that much.) And the heaviest drinkers had a little more than two medium glasses of wine or two beers every night of the week, plus a little more on weekends.

What do the results mean?  The researchers said that  they don't have any evidence linking the brain changes they saw on the MRI brain scans to any negative general cognitive effects, but they did lose more "language fluency" with time. (They gave the people various tests.) The abstainer group (37 people) was very small - perhaps other lifestyle factors (e.g., nutrition) may be playing a part in the results. Also, if people  under-reported actual alcohol consumption - then it would throw off the results. While studies show that drinking can increase cancer risk, other studies have found that moderate drinkers seem to live longer than abstainers. From Medical Xpress:

Even moderate drinking linked to a decline in brain health, finds study

Alcohol consumption, even at moderate levels, is associated with increased risk of adverse brain outcomes and steeper decline in cognitive (mental) skills, finds a study published by The BMJ today. Heavy drinking is known to be associated with poor brain health, but few studies have examined the effects of moderate drinking on the brain—and results are inconsistent. So a team of researchers based at 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 used data on weekly alcohol intake and cognitive performance measured repeatedly over 30 years (1985-2015) for 550 healthy men and women who were taking part in the Whitehall II study. This study is evaluating the impact of social and economic factors on the long term health of around 10,000 British adults. Participants had an average age of 43 at the start of the study and none 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 these confounders, 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.

While those consuming over 30 units a week were at the highest risk compared with abstainers, 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 7 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 (how many words beginning with a specific letter can be generated in one minute). But no association was found with semantic fluency (how many words in a specific category can be named in one minute) or word recall. The authors point out that this is an observational study, so no firm conclusions can be drawn about cause and effect, and say some limitations could have introduced bias. [Original study.]

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