Even Moderate Alcohol Consumption May Harm the Brain

Fran Lowry

June 07, 2017

Moderate drinking is associated with pathologic findings in the brain, including hippocampal atrophy, vs no drinking, new research shows.

Higher alcohol intake also predicted faster decline in cognitive measures of lexical fluency, although not semantic fluency or word recall, researchers found.

"In this study, we found that moderate drinking, within US safe limits, was associated with multiple adverse structural brain outcomes and faster cognitive decline, rather than being protective," lead author, Anya Topiwala, MD, Department of Psychiatry, University of Oxford, Warneford Hospital, United Kingdom, told Medscape Medical News. No protective effect was seen with light alcohol intake.

The findings are published online June 6  in BMJ.

The results support the recent reduction in alcohol guidance in the United Kingdom and call into question the limits currently recommended in the United States, the researchers write.

"Alcohol might represent a modifiable risk factor for cognitive impairment, and primary prevention interventions targeted to later life could be too late," the researchers conclude.

Guidelines from the American Heart Association advise one drink per day for women and one to two drinks per day for men. (A drink is defined as 12 ounces of beer, 4 ounces of wine, 1.5 ounces of 80-proof spirits, or 1 ounce of 100-proof spirits.)

In the United Kingdom, the chief medical officer recently changed the guidelines for low-risk drinking from 21 units to no more than 14 units per week for both men and women because of accumulating evidence that even light drinking increases risk for cancer. The guidelines define 1 unit as 10 mL or 8 g of pure alcohol.

The question of whether moderate alcohol consumption is harmful or protective to the brain "was a really interesting and important one, particularly because so many people drink this amount," Dr Topiwala said.

"There were a few studies reporting that a little alcohol staves off dementia, but the few brain imaging studies were conflicting in their results. The Whitehall II cohort, with its 30 years of rich data on drinking, and many other things, seemed like a perfect group to investigate this important question," she said.

The Whitehall II study was established in 1985 at University College London to investigate the relation between socioeconomic status, stress, and cardiovascular health in over 10,000 nonindustrial civil servants.

Dr Topiwala and her group randomly selected 550 people from this study for the current Whitehall II imaging substudy to determine whether self-reported alcohol consumption over a 30-year period was associated with brain imaging and memory decline.

The mean age of the study participants was 43 years at baseline (standard deviation, 5.4 years), none were alcohol dependent, and all were safe to undergo multimodal MRI of the brain at follow-up.

The participants completed questionnaires and had clinical examinations approximately every 5 years over the study period and had detailed brain scans with MRI at the end.

After adjusting for possible confounding factors, such as age, sex, education, social class, physical and social activity, smoking, stroke risk, and medical history, the researchers found that the people who drank more than the 30 years had higher odds of hippocampal atrophy — shrinkage in the part of the brain that is important for memory and commonly found in Alzheimer's disease — compared with those who did not drink.

The risk was dose dependent, with those who consumed more than 30 units of alcohol per week having the highest risk compared with abstainers (odds ratio [OR], 5.8; 95% confidence interval [CI], 1.8 - 18.6; P ≥ .001).

The risk was also higher among people who drank moderately (14 to 21 units per week). These individuals had 3 times the odds of right-sided hippocampal atrophy (OR, 3.4; 95% CI, 1.4 to 8.1; P = .007).

There was no protective effect in reducing the odds of atrophy of light drinking, defined as 1 to 7 units per week, over abstinence.  

Higher alcohol use was also associated with differences in corpus callosum microstructure and faster decline in lexical fluency, or the number of words starting with the same letter that people can generate in 1 minute.

"The corpus callosum is the large white matter tract, or cabled set of wires, that connects the 2 halves of the brain. One of the brain images we did enabled us to estimate the quality of those fibers, or in other words, how good their insulation was. As people get older, or have problems with their brain blood vessels, this insulation quality reduces. This means nerve impulses are transmitted less efficiently, and this has been linked to reduced memory performance," Dr Topiwala said.

Specifically, higher average alcohol consumption across the study "was inversely associated with white matter integrity…reflected by lower corpus callosum fractional anisotropy and higher radial, axial and mean diffusivity," the authors write. "These associations were focused on the anterior corpus callosum (genu and anterior body)."

Dr Topiwala said she hopes their study spotlights the popular conception that moderate drinking protects against cognitive decline.

"Clearly, ideally guidelines are written on the basis of a wealth of evidence, but this is one piece of evidence that suggests current US drinking guidelines, particularly for men, may need modification. We also need further research in the area to see if similar findings are found in different groups of people."

Doctors should probably avoid suggesting moderate drinking to their patients, Dr Topiwala added.

"On the basis of this study, I would suggest they do not advocate moderate drinking as a strategy to protect against memory decline. In my personal clinical practice, I will be advising my patients drinking over 14 units weekly this may not be safe for their brain health," she said.

In an accompanying editorial,  Killian A. Welch, Royal Edinburgh Hospital, Scotland, writes that the current study's report of adverse effects even at lower levels of alcohol consumption, as well as the finding that drinking more than 14 units per week was associated with both brain pathology and cognitive decline, "provides further support for the chief medical officer's recent decision" to lower recommended levels of alcohol consumption.

"As intake increases, so does the risk to health, probably in a dose dependent manner. Heavy consumption is associated with potentially severe impairments in memory and executive function, even when other obvious risk factors are absent," Dr Welch writes.

"Topiwala and colleagues' findings strengthen the argument that drinking habits many regard as normal have adverse consequences for health. This is important. We all use rationalisations to justify persistence with behaviours not in our long term interest. With publication of this paper, justification of 'moderate' drinking on the grounds of brain health becomes a little harder," he concludes.

The study was funded by UK Medical Research Council, the Gordon Edward Small's Charitable Trust, and the HDH Wills 1965 Charitable Trust. Dr Topiwala and Dr Welch have disclosed no relevant financial relationships.

BMJ. Published online June 6, 2017. Abstract, Editorial

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