JAMA Network Open has recently published the results of an imaging study detailing the association between iron deficiency (ID) without anemia and several markers of brain development among adolescents. ID without anemia is often defined by ferritin levels, though the cut-off is still a matter of debate; a ferritin < 15 ng/mL was the criterion set in this study, though < 25-50 ng/mL has also been suggested. In the U.S., nearly 40% of females between ages 12 to 21 have a ferritin < 15 ng/mL, while approximately 78% have a ferritin < 50 ng/mL, indicating this is a very prevalent condition. The final sample in this cross-sectional study included 209 adolescents with a mean age of 13.5, 58% of whom were female, 30% with ID without anemia, and included children with depression, anxiety, or no psychopathology.
Studies continue to suggest that there are consequences of ID even without anemia in a variety of organs, and this study aimed to help capture the effects in the brain, particularly the basal ganglia (BG), a region where iron naturally accumulates. Adolescents with ID without anemia were found to have a lower content of iron (“lower susceptibility”) in the BG, with a greater magnitude among older children (possibly because of a longer duration of ID), especially girls. Functional and structural changes in the brain were also observed in this study, with susceptibility inversely associated with the volume of structures in the BG and psychiatric symptom severity, and positively with neuropsychological performance. Given that this was a cross-sectional study, causality cannot be determined, but it certainly suggests that ID without anemia poses a risk for impaired brain development among adolescents, as well as psychiatric symptoms and decreased cognitive function.