Effect of iron supplementation on incidence of infectious illness in children: systematic review

Abstract

Objective: To evaluate the effect of iron supplementation on the incidence of infections in children.

Design: Systematic review of randomised controlled trials.

Data sources: 28 randomised controlled trials (six unpublished and 22 published) on 7892 children.

Interventions: Oral or parenteral iron supplementation or fortified formula milk or cereals.

Outcomes: Incidence of all recorded infectious illnesses, and individual illnesses, including respiratory tract infection, diarrhoea, malaria, other infections, and prevalence of positive smear results for malaria.

Results: The pooled estimate (random effects model) of the incidence rate ratio (iron v placebo) was 1.02 (95% confidence interval 0.96 to 1.08, P=0.54; P<0.0001 for heterogeneity). The incidence rate difference (iron minus placebo) for all recorded illnesses was 0.06 episodes/child year (-0.06 to 0.18, P=0.34; P<0.0001 for heterogeneity). However, there was an increase in the risk of developing diarrhoea (incidence rate ratio 1.11, 1.01 to 1.23, P=0.04), but this would not have an overall important on public health (incidence rate difference 0.05 episodes/child year, -0.03 to 0.13; P=0.21). The occurrence of other illnesses and positive results on malaria smears (adjusted for positive smears at baseline) were not significantly affected by iron administration. On meta-regression, the statistical heterogeneity could not be explained by the variables studied.

Conclusion: Iron supplementation has no apparent harmful effect on the overall incidence of infectious illnesses in children, though it slightly increases the risk of developing diarrhoea.

Figures

Figure 1

Funnel plot of extracted studies

Figure 2

Forest plot for incidence rate ratio for all recorded illnesses

Figure 3

Forest plot for odds ratio of malarial parasitaemia (positive results on blood smear test) at end of supplementation period