Effect of Oral Iron Supplementation on Cognitive Function among Children and Adolescents in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis
Chen Z, Yang H, Wang D, Sudfeld CR, Zhao A, Xin Y, Chen JC, Fawzi WW, Xing Y, Li Z · 2022
grade Cmeta-analysisindependentreplicated
Sample
9 studies, 1,196 participants, from five countries
Population
Children and adolescents aged 5-19 in low- and middle-income countries. Registered PROSPERO CRD42020179064.
Design
Random-effects meta-analysis of iron supplementation RCTs restricted to LMICs, with subgroup and meta-regression analysis of dose. Pools nine trials with 1,196 participants - a smaller and more narrowly scoped pool than the 13-trial school-age meta that is cited in the topic.
Key findings
Iron improved intelligence test scores (SMD 0.47, 95% CI 0.10 to 0.83), with meta-regression showing larger gains at higher dose (OR 1.02, 95% CI 1.00 to 1.04). No significant effect on attention, short-term memory, long-term memory, or school performance. The pattern - intelligence-test gains without school-performance gains - is identical to the larger school-age meta.
Genetic confound
None internally (randomized trials). The population is LMIC by construction, so the estimate is not transportable to well-nourished children.
DOI / URL
Effects
| Outcome | Metric | Value | Measure | Timing | Vs | Horizon | Class |
|---|---|---|---|---|---|---|---|
| Intelligence test scores (near g) | pooled SMD | 0.47 (95% CI 0.10 to 0.83) | standardized | end of supplementation | business-as-usual | end-of-treatment | g |
| School performance (domain skills) | pooled SMD | no significant effect | standardized | end of supplementation | business-as-usual | end-of-treatment | domain-skill |
| Attention, short-term memory, long-term memory | pooled SMD | no significant effects | mixed | end of supplementation | business-as-usual | end-of-treatment | near-transfer |