Drinking more than four alcoholic beverages a week may lead to increased iron accumulation in the brain and subsequent neurological declines in executive function, fluid intelligence and reaction time, according to a new study published in PLOS Medicine.
In what may be the largest study to date to examine the impact of moderate alcohol consumption upon iron homeostasis, researchers employed susceptibility-weighted magnetic resonance imaging (MRI) to determine iron content of brain regions and liver tissues in 20,729 study participants. According to the study, the average weekly alcohol consumption was 17.7 units (141.6 grams) and never drinkers accounted for 2.7 percent of the study population.
The researchers found a higher susceptibility of iron accumulation in the bilateral putamen and caudate structures and the substantia nigra region of the brain among study participants who consumed alcohol, according to the study. With the exception of the thalamus, the study authors noted that drinking more than seven units of alcohol a week (56 grams or four alcohol drinks) led to higher susceptibility for iron accumulation “for all brain regions.”
“Alcohol consumption, including at low levels, was observationally associated with higher brain iron in multiple basal ganglia regions,” wrote study co-author Thomas E. Nichols, PhD, a professor of neuroimaging statistics in the Nuffield Department of Population Health at the Big Data Institute at the University of Oxford in the United Kingdom, and colleagues. “ … Markers of higher brain iron (higher susceptibility) were associated with poorer executive function and fluid intelligence and slower reaction speed.”
When it came to assessing executive function via a neuropsychological trails making test (TMT), Nichols and colleagues noted the impact of age in interactions with bilateral putamen, bilateral caudate and right hippocampal susceptibility to higher iron deposition. They also found that slower simple reaction time was associated with higher bilateral pallidum and right substantia nigra susceptibility.
The study authors pointed out that postmenopausal status did not have any effect on the association between alcohol consumption and brain iron in a study population nearly evenly divided by men and women (48.6 percent), 70 percent of whom were postmenopausal.
In regard to study limitations, alcohol use was self-reported via touchscreen questionnaire. The study authors also acknowledged that susceptibility and liver tissues may possibly be affected by myelin as well as iron, and that alcohol exposure prior to study initiation may have led to possible bias with estimates in the observational study.