Author Affiliation: Department of International Nutrition, Center for Human Nutrition, The Johns Hopkins Bloomberg School of Public Health, Baltimore,<?xpp j?> Maryland.
In this issue of the Archives, Lozoff et al1 report the findings of a long-term follow-up of children at 10 years of age who were participants in a double-masked, randomized controlled trial conducted from 1991 through 1994 in Santiago, Chile, testing iron-fortified (12.7 mg/L) vs low-iron (2.3 mg/L) infant formula use from 6 to 12 months of age.2 All infants enrolled in the original trial were screened to have no iron deficiency anemia at the outset. Among 57% of the original sample of children who were reached, an intent-to-treat analysis showed that the mean scores on tests of spatial memory and visual-motor integration at 10 years of age were lower in the iron-fortified group compared with the control.1 The mean effect sizes for both these outcomes were small (−0.21), whereas effect sizes for other measures, such as overall IQ, arithmetic, visual perception, and motor coordination, showing a similar negative trend were even smaller, ranging from −0.08 to −0.16, and not significant. Stratified analyses revealed large negative effect sizes (−0.85 to −1.36) of the iron formula among children who had high hemoglobin (Hb) levels (Hb level >12.7-13.0 g/dL, 5.0%-5.5% of the sample) at the start of the trial, whereas those with low Hb level (<10.4-10.7 g/dL, 9%-24% of the sample) benefitted somewhat with the intervention. For a large proportion of children with Hb concentrations in the middle of the distribution (10.8-12.7 g/dL, 70%-90% of the sample) the iron intervention did not have any impact on the measured outcomes. (To convert Hb to grams per liter, multiply by 10.0.)
Christian P. Iron in Infancy and Long-term Development. Arch Pediatr Adolesc Med. 2012;166(3):285-286. doi:10.1001/archpediatrics.2011.203