Moderate drinking associated with cognitive decline, study finds

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New research from the United Kingdom has found that consumption of seven or more units of alcohol per week is associated with higher iron levels in the brain, which has been linked with Alzheimer’s and Parkinson’s diseases, as well as cognitive decline. In the UK, one unit equals eight grams of ethanol, according to the study.

The study, published in the journal, PLOS Medicine, was led by Anya Topiwala, DPhil, of the University of Oxford in the United Kingdom. Topiwala and her research team sought to investigate evidence in support of causal relationships between alcohol consumption and brain iron levels and to assess whether higher brain iron represents a potential pathway to alcohol-related cognitive deficits.

To do this, they engaged 20,965 participants in a United Kingdom cohort study, and explored the relationships between self-reported alcohol consumption and brain iron levels by using magnetic resonance imaging (MRI), the study said. Participants' mean age was 55 years old, and 48.6 percent were female. Although 2.7 percent classified themselves as non-drinkers, the average intake was around 18 units per week, which translates to about 7.5 cans of beer or six large glasses of wine.

Almost 7,000 of the participants also had their livers documented using an MRI to assess levels of systemic iron, according to the study. All individuals completed a series of tests to assess cognitive and motor function. Researchers evaluated the association of alcohol intake with blood and liver iron and cognitive measures associated with higher brain iron.

The investigators found that alcohol consumption with more than seven units weekly was linked with markers of increased iron in the basal ganglia, a group of brain regions connected to controlling motor movements, procedural learning, eye movement, cognition, and emotion.

Although drinking was self-reported and could be underestimated, according to the authors, this was considered the only feasible method to establish such a large cohort's intake. A limitation of the work is that MRI-derived measures are indirect representations of brain iron and could conflate other brain changes observed with alcohol consumption with changes in iron levels.