Objective: To evaluate the effect of iron supplementation on mental and motor development in children through a systematic review of randomised controlled trials (RCTs).
Data sources: Electronic databases, personal files, hand search of reviews, bibliographies of books, abstracts and proceedings of international conferences.
Review methods: RCTs with interventions that included oral or parenteral iron supplementation, fortified formula milk or cereals were evaluated. The outcomes studied were mental and motor development scores and various individual development tests employed, including Bayley mental and psychomotor development indices and intelligence quotient.
Results: The pooled estimate (random effects model) of mental development score standardised mean difference (SMD) was 0.30 (95% confidence interval (CI) 0.15 to 0.46, P<0.001; P<0.001 for heterogeneity). Initial anaemia and iron-deficiency anaemia were significant explanatory variables for heterogeneity. The pooled estimate of Bayley Mental Development Index (weighted mean difference) in younger children (<27 months old) was 0.95 (95% CI -0.56 to 2.46, P=0.22; P=0.016 for heterogeneity). For intelligence quotient scores (> or =8 years age), the pooled SMD was 0.41 (95% CI 0.20 to 0.62, P<0.001; P=0.07 for heterogeneity). There was no effect of iron supplementation on motor development score (SMD 0.09, 95% CI -0.08 to 0.26, P=0.28; P=0.028 for heterogeneity).
Conclusions: Iron supplementation improves mental development score modestly. This effect is particularly apparent for intelligence tests above 7 years of age and in initially anaemic or iron-deficient anaemic subjects. There is no convincing evidence that iron treatment has an effect on mental development in children below 27 months of age or on motor development.