Relating iron status and aerobic fitness to cognitive performance in young adult females
Open Access
- Author:
- Scott, Samuel Pew
- Graduate Program:
- Nutritional Sciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 10, 2015
- Committee Members:
- Laura E Murray Kolb, Dissertation Advisor/Co-Advisor
Laura E Murray Kolb, Committee Chair/Co-Chair
Shannon Leanne Kelleher, Committee Member
A Catharine Ross, Committee Member
Rick Owen Gilmore, Committee Member
Jere Haas, Special Member - Keywords:
- Iron
nutrition
cognition
brain
fitness
physical performance - Abstract:
- Iron deficiency (ID) is the most prevalent single micronutrient deficiency worldwide, with women of reproductive age (WRA) being disproportionately affected due to menstrual iron losses. Previous research has demonstrated a critical role of iron in early-life brain development and function but few studies have examined this relation in WRA, despite continued reliance on neural processes shown to be impacted by iron supply such as dopaminergic signaling. Even less evidence exists regarding whether cognitive alterations manifest during mild ID without anemia. Similarly, though a strong link between exercise and brain health has been shown, little work has documented how physical fitness in WRA relates to cognition, a troubling fact given that 40-50% of WRA in the United States are physically inactive. We sought to explore interrelations between iron status, physical fitness, cognition, and academic performance in WRA within a university setting, where optimal cognitive functioning has direct implications for current livelihood and future wellbeing. This observational study involved 127 generally healthy, non-anemic females aged 18-35 years (average 22 years). Each woman underwent a blood draw to assess iron status, a maximal exercise test to assess cardiorespiratory fitness, and five computerized cognitive tests of executive function—Attentional Network Task, Berg’s Card Sorting Task, Go/No-Go, Sternberg Memory Search, and Tower of London—using the Psychology Experiment Building Language platform. The sample was selected for low ferritin levels, with 40% having Ft ≤ 12 µg/L. Fitness was generally high, with an average peak VO2 of 44.5 ml/min/kg, corresponding to the American College of Sports Medicine’s 80th-85th percentile for females aged 20-29 years in the United States. After controlling for a set of potential covariates, results suggested that executive function remains largely intact in mild ID, with one exception being planning ability as measured using the Tower of London task. Positive associations were found between fitness and performance measures on four of the five cognitive tasks, suggesting that fitness widely benefits executive ability. No added cognitive benefit of concurrent high iron status and high physical fitness was found. However, grade point average (GPA) was positively associated with both iron status and fitness such that a group with concurrent ID and lower fitness had the lowest GPA, whereas a group with concurrent iron sufficiency and higher fitness had the highest GPA. Furthermore, better academic performance was found in women with higher scores on a latent factor representing high-level executive processes. In conclusion, this study has expanded the knowledge base in two underexplored areas with public health relevance: how both mild ID and physical fitness impact cognition in healthy young adult females. Our findings support earlier work showing that most cognitive components remain intact during early ID, but that certain aspects may be negatively impacted. Additionally, the current study extends previous research by showing that cardiorespiratory fitness in WRA is related to multiple executive tasks known to recruit fronto-parietal circuits. We are the first to demonstrate that iron status in WRA is related to academic performance, and this observation alone deserves further consideration given the number of ID individuals worldwide.