Drinking even a moderate amount of alcohol — 7 alcoholic beverages a week — may cause cognitive decline according to a study in PLoS Medicine.

Previous studies have connected high brain iron levels with Alzheimer disease and Parkinson disease. Observational research suggests an association with brain iron levels and heavy alcohol use.

To find out if the same connection exists in moderate drinkers, the researchers used data from the UK Biobank study and follow-up diagnostics. After collecting data from surveys and MRIs, they categorized weekly alcohol consumption into quintiles and reviewed MRI images. Mendelian randomization was used to estimate the association between genetic predisposition and brain susceptibility, among other factors.


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The researchers found that adults who drank more than 7 units of alcohol weekly were more susceptible to higher iron levels in all brain regions except the thalamus. Less than 7 units weekly was not associated with higher brain iron. Adjustment for red meat consumption and iron supplementation did not alter the results. Drinking more than 11 units weekly in men and 17 or more for women was associated with higher liver iron.

Of the study limitations, some of the results observed on MRI could reflect myelin changes. Also, alcohol use was self-reported, which could impact accuracy.

“Alcohol-related brain iron may be partially mediated by higher systemic iron levels, but it is likely there are additional mechanisms involved,” researchers concluded.

“Poorer executive function and fluid intelligence and slower reaction speeds were seen with markers of higher basal ganglia iron. Moderate drinking is highly prevalent, so if elevated brain iron is confirmed as a mechanism by which alcohol leads to cognitive decline, there are opportunities for intervention on a population scale.”

Reference

Topiwala A, Wang C, Ebmeier KP, et al. Associations between moderate alcohol consumption, brain iron, and cognition in UK Biobank participants: observational and Mendelian randomization analyses. PLoS Med. 19(7): e1004039. doi:10.1371/journal.pmed.1004039