Attention Mediates the Relationship Between Iron Status and Physical Performance in Chinese University Women

Background Both iron deficiency (ID: serum ferritin (sFer)< 15μg/L) and ID anemia (IDA: sFer<15μg/L + hemoglobin (Hb)< 120g/L) are highly prevalent in China, affecting over 20% of women and 30% of children under two. It is well established that ID impairs physical performance in adults. But recently, ID has also been shown to negatively affect cognitive functions such as attention and memory, as well as motivation. However, the relationships connecting cognition, iron status, and physical performance remain unclear. A cross‐sectional study that measures physical performance in combination with cognitive and motivational measures in ID and IDA Chinese subjects could illuminate potential interactions between these three factors. We tested the hypothesis that attention mediates the relationship between iron status and physical performance by assessing the extent to which a set of alternative regression‐based conditional process models could account for three physical performance measures: estimated VO 2 max, energy expended, and total time on the endurance trial. Objective To assess the relationship between iron status and attention in modifying physical performance. Methods 54 women were screened for a cross‐sectional study, of which 48 were found to be ID, IDA or healthy and were included in the study. Each subject completed a physical activity questionnaire, anthropometric measurements, a resting blood draw, and two physical performance tests on a cycle ergometer: a submaximal VO 2 assessment to estimate VO 2 max and energy expended at a fixed relative work load, and an endurance test to voluntary cessation of pedaling at a workload equivalent to 75% of estimated VO2max. In addition, participants completed two tasks intended to assess both low‐ and high‐level aspects of attentional control. The first was a go/no‐go (GNG) task, in which participants pressed a key in response to one stimulus (e.g., horizontally aligned bar) presented in 20% of the trials and withheld a response given a second stimulus (e.g., vertically aligned bar) presented in 80% of the trials. The second was an attentional network (ANT) task, in which participants indicated the direction of a centrally‐presented arrow, which was flanked by consistent, inconsistent, or neutral stimuli and preceded by informative or uninformative cues. We identified a model in which the relationship between sFer and physical performance (R2 = .36, .46, .19 for VO2max, energy expended, total time) was mediated by attention (as measured by reaction times in the GNG and ANT, R2 = .17, .20, respectively), and in which Hb modified the relationship between sFer and the measures of both attention and physical performance. This model was shown to be superior (in terms of proportion of variance accounted for and significance of parameter estimates) to alternative models, including ones in which attention played no role and ones in which the directionality of the relationships was reversed. Conclusions The results suggest the importance of cognitive abilities in physical performance and the manner in which variations in iron status may affect both. Support or Funding Information Cornell Lehman Fund, Cornell Mario Einaudi Travel Grant