Effects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis

Iron deficiency in infants and children - the current research challenges

PURPOSE OF REVIEW

Iron deficiency (ID) affects one in five children before they reach preschool age. Existing evidence on ID contributing to suboptimal development and neurodevelopmental disorders come mostly from mechanistic and observational studies. Recommendations for screening and treatment are diverging, emphasizing the knowledge gap. The purpose of this review is to summarize recent evidence on ID in infants and children, its possible role in developmental disorders, and effects of iron supplementation.

RECENT FINDINGS

Recent well powered randomized controlled trials showed no effect of early iron supplementation on psychomotor development in infants, neither in populations at high nor low risk of ID. Treatment of nonanemic ID in children 1-3 years did not improve their cognitive scores. Evidence from observational and imaging studies suggests association of brain ID and attention deficit hyperactivity disorder in children (ADHD).

SUMMARY

Universal prophylactic iron supplementation in infants is not supported by current evidence. Whether non anemic ID needs to be treated is uncertain and so is the legitimacy and timing of screening for ID and anemia. The role of ID and iron availability for the brain in pathogenesis of neurodevelopmental conditions such as ADHD requires further studies.

Management of iron deficiency in children, adults, and pregnant individuals: evidence-based and expert consensus recommendations

Iron deficiency is the most common micronutrient deficiency worldwide. Oral iron is often recommended as first-line treatment, but there is no consensus on the optimal formulation, dosing strategy, or which patients should be treated preferentially with intravenous iron. To address these challenges, the Iron Consortium at Oregon Health & Science University (OHSU) convened an international panel of 26 experts in haematology, primary care, paediatrics, obstetrics, gastroenterology, cancer, and patient advocacy among its members. This panel was supplemented by insights from a four-person patient focus group to develop current recommendations using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. The panel developed clinically relevant questions in five priority topic areas, a systematic literature search was performed, and studies meeting a priori criteria were included to generate evidence tables for recommendation development. Evidence-based and expert opinion-based recommendations were made through a structured anonymous consensus voting process at an in-person meeting in Portland, OR, USA, hosted by OHSU on Feb 16-17, 2024. The expert panel made seven evidence-based recommendations for three demographic groups with iron deficiency: non-pregnant adults, pregnant individuals, and infants, children, and adolescents. Expert opinions supported the recommendations on 21 aspects of care for which there is insufficient evidence. This Review provides evidence-based recommendations and expert consensus on the diagnosis, treatment, and management of iron deficiency, detailing best practices for oral and intravenous iron repletion across diverse patient populations.

Detection of Anemia in Schoolchildren Aged 6-18 Years With Hematocrit Percentile Charts and the Impact of Economic Status in Southern Brazil

OBJECTIVE

To generate hematocrit percentile charts for schoolchildren aged 6-18 years and determine the prevalence of anemia by socioeconomic status class in southern Brazil.

METHODS

This is a cross-sectional study utilizing data collected between 2014 and 2017 from southern Brazil. The study's sample consists of 4802 schoolchildren, aged 6 to 18 years. The percentile charts for sex-specific hematocrit were developed using the LMS (Lambda-Mu-Sigma) method. The simplified economic classification, based on ABEP criteria, was used to group individuals into A + B (high), C (middle), and D + E (low) income classes. Anemia was defined as hematocrit z-score ≤ -1.96 for age and sex.

RESULTS

Among boys, 58 (2.86%) were anemic, 1955 (94.81%) had normal hematocrit levels, and 48 (2.33%) had high hematocrit. Girls showed a similar pattern, with 73 (2.73%) anemic, 2534 (94.90%) with normal hematocrit, and 63 (2.36%) with high hematocrit. For girls, a higher prevalence of non-anemic hematocrit was observed in class A (39.33%) compared to anemic children (23.28%), with significant standardized residuals. For boys, significant residuals were observed for a higher prevalence of anemic children in the lower socioeconomic class DE (13.79%) compared to non-anemic children (5.18%), and a higher prevalence of non-anemic children in the upper socioeconomic class A (42.63%) compared to anemic children (22.41%).

CONCLUSION

The percentile charts generated from hematocrit levels enabled the comparison of anemia prevalence across socioeconomic status classes. A higher prevalence of anemia was found among boys in lower socioeconomic classes, while girls in higher socioeconomic classes showed a lower prevalence of anemia.

Anemia: Etiology, Pathophysiology, Impact, and Prevention: A Review

Background

Anemia is a significant public health problem worldwide in rich and poor countries. Anemia among teenagers can be seriously almost entirely caused by a lack of substance iron, which is closely related to the level of severity of anemia. The most visible effect of anemia is a decline in achievement studying in school. This article briefly introduces anemia, etiology, pathophysiology, impact, and preventive measures.

Methods

Major databases, including Scopus, Pubmed, Proquest, Google Scholar, and Science Direct, were researched to obtain articles related to anemia in adolescent girls. The keywords used in the literature search were " anemia and teenage girls "and " anemia prevention. " The time frame of the articles obtained ranged from 2012 to 2023.

Results

Enhancement observed prevalence during several final years will cause prevalence to exceed the agreed target level. The most visible impact of anemia is a decline in achievement studying in school. Not only that, teenage women who suffer from anemia are at risk of experiencing anemia during pregnancy, which can hurt the growth and development of the fetus in Content. Apart from that, there is the potential to experience complications during pregnancy and childbirth.

Conclusion

Identifying and understanding the etiology of anemia is critical to developing effective prevention strategies with screening. An integrated approach to early prevention of anemia involves collaboration between the health, education, and community sectors.

The alterations of sleep and frontal functions in chronic hemodialysis: Pathogenesis and therapeutic perspectives

Chronic kidney disease (CKD) and, in particular, chronic haemodialysis (HD) patients have a high risk of developing sleep disorders and executive dysfunction. Sleep disorders have a prevalence of 75 % in the haemodialysed population and several causes are behind their occurrence: sympatho-vagal imbalances, low melatonin production, vitamin D deficiency, altered cerebral haemodynamics and haemodialysis-induced vascular stress. Executive dysfunction affects about 55 % of haemodialysis patients. The causes can be ascribed to dysfunctions of the frontal lobes. HD patients show frontal brain atrophy and reduced brain activity and connectivity of several frontal and prefrontal areas. Sleep quality also has a significant impact on executive functions; inefficient and fragmented sleep reduces the efficiency of executive functions and increases the risk of dementia. Sleep deprivation also alters the connectivity and structure of several frontal areas. Thus, sleep and executive functions seem to be closely linked. Multidisciplinary care of patients with CKD and in HD appears essential to structure preventive interventions, pharmacological and non-pharmacological treatments that can improve sleep quality, preserve the integrity of executive functions and improve their quality of life.

Neonatal sevoflurane exposures inhibits DHHC5-mediated palmitoylation of TfR1 in oligodendrocytes, leading to hypomyelination and neurological impairments

INTRODUCTION

Neonatal anesthesia-related neurological impairments are of significant concern, closely linked to oligodendrocyte dysfunction. However, there is a notable temporal discrepancy between the sustained development of oligodendrocytes (myelination) and the short-term vulnerability to anesthesia exposures.

OBJECTIVES

Given the significant rise in iron demand by oligodendrocytes during neonatal period, our objective was to clarify the potential roles and underlying mechanisms of iron homeostasis, particularly focusing on transferrin receptor 1 (TfR1), in governing the transient susceptibility to anesthesia.

METHODS

Sevoflurane (3 %, 2 h/day) was administered to wildtype or Pdgfrα-CreERT mice from postnatal day (P)6 to P8. Subsequently, behavioral tests, genetic modulation, co-immunoprecipitation assays, Acyl-resin assisted capture assay and single-cell RNA sequencing were employed on P8 and/or P32.

RESULTS

Following neonatal exposure to sevoflurane, the observed cognitive impairments and hypomyelination at P32 were attributed to iron accumulation and ferroptosis, particularly within oligodendrocytes of the corpus callosum (CC). This ferroptosis was mediated by enhanced endocytosis of transiently expressed TfR1, rather than its overexpression, due to inhibited palmitoylation. Among the 21 palmitoyltransferases, only Asp-His-His-Cys5 (DHHC5) was down-regulated in oligodendrocytes, reducing palmitoylation of TfR1 at the C98 cysteine site. Furthermore, specific overexpression of DHHC5 in oligodendrocytes significantly restored TfR1 endocytosis, hypomyelination, and ferroptosis, thereby preventing neuronal ferroptosis across multiple brain regions by decreasing iron transport, ultimately mitigating neurological impairments.

CONCLUSION

We discovered that decreased DHHC5 in oligodendrocytes promotes TfR1 associated ferroptosis, resulting in hypomyelination and initiating neuronal ferroptosis, thereby impairing cognition following neonatal sevoflurane exposures. The transiently expressed TfR1 may mediate the critical period for neonatal anesthesia vulnerability. These findings highlight the pivotal role of TfR1-associated ferroptosis in neonatal anesthesia-associated neurotoxicity and oligodendrocyte-neuron interaction, while providing new perspect to understand temporary neurotoxicity of anesthesia. DHHC5 may represent promising therapeutic target to enhance the safety of neonatal anesthesia and iron-related oligodendrocytes disorders.

The effect of fruits and vegetables on children's mental and cognitive health: A systematic review of intervention studies and perspective for future research

OBJECTIVES

To synthesize evidence from fruit and vegetable intervention studies investigating mental or cognitive health outcomes (or both) in children ≤10 y. Our aim was to understand the efficacy of such interventions in improving measures of cognitive performance or mental health and to identify successful intervention elements to inform future research.

METHODS

We conducted a systematic search of the Cochrane, Embase, PubMed, and CINAHL databases for articles published before August 2022 (PROSPERO registration no. CRD42022356571). A narrative synthesis was conducted according to the Synthesis Without Meta-Analysis guidelines.

RESULTS

Of the 4686 articles identified, only 7 of the 17 full texts screened were included in the final review. No studies investigated the efficacy of interventions using "whole" fruits or vegetables. Six studies examined the effects of blueberries using drinks made from fresh (1 cup) or freeze-dried (30 g) blueberries and one study evaluated a mulberry powder-based drink. Sample sizes ranged from 14 to 54, and most studies were acute interventions with outcomes measured in a 2- to 3-h window (n = 6). Through a narrative synthesis of direction of responses, measures of executive function appeared sensitive to intervention effects in both acute and longer-term settings. Some concerns of risk of bias were evident, according to the RoB 2 tool, related to incomplete reporting of methodological aspects.

CONCLUSIONS

The studies identified through this systematic review could not directly address the planned research question, resulting in poor certainty of evidence. Future research with whole fruit and vegetable interventions could better inform population health strategies for improved mental and cognitive health outcomes in children.

Associations between Serum Iron Indices and Self-Assessed Multiple Intelligence Scores among Adolescents in Riyadh, Saudi Arabia

Micronutrient deficiencies, including iron deficiency, are linked to different cognitive impairments and sensory functions. However, whether circulating iron levels affect self-assessed multiple intelligence (MI) scores in adolescents remains uninvestigated. This study aimed to investigate associations between serum iron levels and self-assessed MI scores in adolescents in Riyadh, Saudi Arabia. Recruiting 434 Saudi adolescents (174 boys and 260 girls, aged 12-17), we administered the McKenzie questionnaire to assess MI across nine categories. Anthropometrics and fasting blood samples were collected to measure circulating iron and transferrin levels. Total iron-binding capacity (TIBC) and transferrin saturation (TSAT) levels were calculated. Notably, girls exhibited significantly higher MI scores in the interactive domain than boys (age and BMI-adjusted OR = 1.36, 95% confidence interval = 1.07-1.73, p = 0.01). No significant correlations were observed between serum iron and MI. However, normal TSAT levels (TSAT > 20%) corresponded with higher age and BMI-adjusted odds of MI scores in the musical (OR = 1.59, 95%CI = 1.1-2.2, p = 0.006), linguistic (1.57, 1.1-2.3, p = 0.016), kinesthetic (1.48, 1.1-2.1, p = 0.024), spatial (1.45, 1.1-2.1, p = 0.03), and existential (1.56, 1.1-2.1, p = 0.01) categories compared to ones with lower TSAT levels (TSAT ≤ 20%), only in boys. In conclusion, serum iron levels may not directly influence MI domains in adolescents in Riyadh, Saudi Arabia; however, lower TSAT levels, indicative of iron-deficiency anemia, may influence MI, only in boys, indicating a possible relationship between iron metabolism and cognitive functions.

Iron status and hemoglobin adjustment by altitude to define anemia in children aged 6 to 8 months living in Lima, Arequipa, Cusco and Puno

OBJECTIVE.

To describe the iron status profile and to propose hemoglobin adjustment factors for altitude for children aged 6 to 8 months in Lima, Arequipa, Cusco and Puno.

MATERIALS AND METHODS.

Cross-sectional study in children aged 6 to 8 months from four cities. We measured hemoglobin and other iron biomarkers, C-reactive protein (CRP), among others. To estimate the adjustment equation, we applied an exponential regression. We excluded children with iron deficiency (ID) and/or inflammation.

RESULTS.

The proportions of ID were higher in Puno and Arequipa, while inflammation did not exceed 19% in any of the cities. Hemoglobin showed an exponential increase at higher altitude. The adjustment equation was: 10.34249 x (1.00007 ^ Alt).

CONCLUSIONS.

Children residing in Arequipa and Puno showed higher rates of ID and lower iron reserves; furthermore, the increase in hemoglobin by altitude was exponential, showing the need to adjust hemoglobin at altitude.

Effectiveness of intermittent iron and high-dose vitamin A supplementation on cognitive development of school children in southern Ethiopia: a randomized placebo-controlled trial

BACKGROUND

Iron is an essential mineral whose deficiency results in cognitive alteration, impaired emotional behaviors, and altered myelination and neurotransmission. In animal models, it has been shown that vitamin A (VA) could affect cognition.

OBJECTIVES

The study aimed to evaluate the effectiveness of intermittent iron and VA supplementation on cognitive development of schoolchildren, and to assess the interaction between these supplementations.

METHODS

Considering a 2 × 2 factorial design, 504 children were randomly assigned to 1 of the 4 arms: placebo VA and placebo iron supplement; high-dose vitamin VA and placebo iron supplement; iron supplement and placebo VA; and iron and high-dose vitamin VA supplements. Cognitive development was assessed using Raven's Coloured Progressive Matrices, digit span, Tower of London, and visual search tasks.

RESULTS

The mean [± standard deviation (SD)] age of the enrolled children was 9.6 (±1.6) y. One-fifth of the children had iron deficiency or anemia, whereas 2.9%, 3.9%, and 12.1% of children had low iron stores, iron deficiency anemia, and VA deficiency, respectively. Intermittent iron supplementation did not result in any significant improvement of children's cognitive development and had a negative effect on the performance index of the visual search task compared with placebo (-0.17 SD, 95% confidence interval: -0.32, -0.02). Effects were evident among children with stunting, thinness, or children coming from understimulating home environments. High-dose VA supplementation resulted in a significant improvement of digit span z-score with a mean difference of 0.30 SD (95% confidence interval: 0.14, 0.46) compared with placebo VA. VA had a more beneficial impact for girls, children infected with helminths, and those from food secure households.

CONCLUSION

In a population where the prevalence of iron deficiency is low, intermittent iron supplementation did not have any or negative effect on the child's cognitive development outcomes. Conversely, VA supplementation improved the child's working memory.

TRIAL REGISTRATION NUMBER

The study is registered at clinicaltrials.gov as NCT04137354 (https://clinicaltrials.gov/study/NCT04137354).