Iron Status Is Associated with Performance on Executive Functioning Tasks in Nonanemic Young Women

Background: Iron deficiency (ID) is prevalent, particularly among women of reproductive age (WRA). How mild ID without anemia relates to cognition is poorly understood. Executive functioning (EF) has emerged as potentially being affected by mild ID in WRA. Objective: We sought to examine how iron markers relate to performance on EF tasks in nonanemic WRA. Methods: Participants included 127 females aged 18-35 y. Hematological indicators included hemoglobin, RBC distribution width, transferrin saturation (TSAT), ferritin, transferrin receptor (TfR), and total body iron (TB I). EF was assessed using 5 tasks. Associations between EF outcomes and iron status were examined using continuous iron predictors and group comparisons. Results: Better iron status was associated with better attention [faster reaction time (RT) with lower TfR (P = 0.028) and higher TSAT (P = 0.013)], inhibitory control [lower RI variability with higher TSAT (P = 0.042) and planning ability (faster planning time and a smaller planning time increase with increasing difficulty with higher ferritin; P = 0.010)]. No associations with iron status were found for several EF outcomes, possibly due to performance ceilings. Paradoxically, worse performance on a working memory task was related to better iron status, which may reflect hippocampal-frontal interference [lower capacity with lower TfR (P = 0.034) and higher TBI (P = 0.043) and a larger accuracy change with increasing difficulty with higher TBI (P = 0.016)]. Longer RTs on a working memory task were observed among those with positive TBI (iron surplus; P = 0.021) and <2 abnormal iron markers (P = 0.013) compared with those with negative TBI (iron deficit) and >= 2 abnormal markers, respectively. Conclusions: These findings suggest cognitive ramifications of mild ID in otherwise healthy WRA and have implications for daily well-being. Future investigators should explore how brain system interactions change according to iron availability.