Drinking more than three beers or about three tall glasses of wine per week is significantly associated with higher iron levels in several brain regions, which is linked to poorer cognitive function.
That’s according to a study from the UK of almost 21,000 people – probably the largest survey of moderate alcohol consumption and iron build-up to date.
Iron buildup in the brain has previously been linked to Parkinson’s disease and other neurodegenerative diseases.
“In the largest study to date, we found that drinking more than seven units of alcohol per week was associated with iron accumulation in the brain,” Anya Topiwala, MD, PhD, said in a statement. . Press release. Topiwala, from the Big Data Institute at the University of Oxford in the UK, is the first author of the study.
“Higher brain iron is in turn linked to lower cognitive performance, such as executive function (problem solving) and fluid intelligence (puzzle tasks),” Topiwala said, adding that “accumulation may underlie alcohol-related cognitive decline”.
These findings shed light on potential underlying mechanisms for alcohol’s negative effects on brain health, the researchers noted.
Klaus Ebmeier, MD, one of the study’s authors and professor of old age psychiatry at the University of Oxford, said: “This is part of a series of Oxford studies carried out in the wider UK biobank dataset that suggests even ‘normal’ alcohol consumption carries a risk for [aging]the mental and physical health of the brain.
“Anyone who consumes alcohol has to balance that against their potential enjoyment of a drink,” Ebmeier added.
The study, “Associations between moderate alcohol consumption, brain iron and cognition in UK Biobank participants: observational and Mendelian randomisation analyzeswas published in the journal OLP Medicine.
A growing body of evidence suggests that even moderate alcohol consumption negatively affects brain health. Topiwala, Ebmeier and colleagues have previously shown that moderate alcohol consumption is a risk factor for negative brain outcomes and cognitive decline.
Effects of too much iron
Although the underlying mechanisms remain largely unknown, iron accumulation in the brain is considered a possible contributor, “because higher brain iron has been described in many neurodegenerative conditions, including Alzheimer’s and Parkinson’s disease” and “in alcohol dependence,” the researchers wrote.
However, it is unclear whether iron levels in the brain differ by level of alcohol consumption.
Now these two researchers, along with colleagues in the UK and US, have assessed potential relationships between alcohol consumption and brain iron levels and whether higher brain iron accumulation represents a potential mechanism of alcohol-related cognitive deficits.
The study included 20,965 participants (48.6% women) from UK Biobanka large-scale database containing genetic and health information of half a million people in the UK who were recruited from 2006 to 2010.
These participants, with an average age of 54.8 years, had declared their own alcohol consumption at the start of the study (baseline). For current drinkers, the total weekly number of UK units of alcohol consumed was calculated by adding together the types of drink.
It should be noted that a unit of alcohol in the UK comprises approximately 8 grams of pure alcohol; a standard American drink contains 14 g.
All participants had their brains scanned by magnetic resonance imaging (MRI) at an average of 9.6 years after baseline; of these, 6,936 also underwent liver MRI. MRI scans were used to indirectly assess iron content in the brain and liver, which in this case was used as a marker of systemic iron or whole-body iron levels.
They also completed a series of simple tests to assess cognitive function at baseline and at online follow-up, at an average of 5.8 years later.
The results showed that 2.7% of the participants considered themselves non-drinkers and the average alcohol consumption per week was 17.7 units, which is about 7.5 cans of beer or six tall glasses of wine.
This consumption was above current UK drinking guidelines to keep its health risks low (less than 14 units per week). US guidelines recommend limiting daily alcohol consumption to two drinks or less for men and one drink or less for women.
Effects on basal ganglia
Drinking more than seven units per week (56 g of pure alcohol) was significantly associated with markers of higher iron levels in the basal ganglia, a group of brain regions involved in movement, higher cognitive functions high such as problem solving and emotion.
Alcohol consumption greater than 11 units per week in men and 17 units in women was significantly related to increased hepatic iron measured by MRI. Additionally, “systemic iron levels partially mediated associations between alcohol consumption and brain iron,” the researchers wrote.
Additionally, iron accumulation in some of these brain regions was significantly associated with poorer cognitive function, namely slower executive function, less ability to solve puzzles, and slower reaction times.
These results indicate that the accumulation of iron in the brain is a potential mechanism behind the negative effects of alcohol on cognitive functions.
Given the prevalence of moderate alcohol consumption, even small links to cognitive decline can have a substantial impact on the population as a whole. As such, interventions aimed at reducing alcohol consumption can benefit the general population.
Among the limitations of the study, the researchers pointed to the indirect measurement of iron levels by MRI, which may be influenced by other factors, and the method of self-reporting of alcohol consumption, which may have led to underestimates. However, the latter was considered the only possible method for determining intake in such a large group of people.
Additionally, “it is unclear how our findings generalize to other populations, particularly those that are more ethnically diverse and socioeconomically disadvantaged,” the team wrote.