RANDOMIZED STUDY OF COGNITIVE EFFECTS OF IRON SUPPLEMENTATION IN NONANEMIC IRON-DEFICIENT ADOLESCENT GIRLS

Background Up to 25% of adolescent girls in the USA are iron deficient . This double-blind, placebo-controlled clinical trial assessed the ef fects of iron supplementation on cognitive function in adolescent girl s with non-anaemic iron deficiency. Methods 716 girls who enrolled at four Baltimore high schools were screened for non-anaemic iron deficie ncy (serum ferritin less than or equal to 12 mu g/L with normal haemog lobin). 98 (13 . 7%) girls had non-anaemic iron deficiency of whom 81 were enrolled in the trial. Participants were randomly assigned oral f errous sulphate (650 mg twice daily) or placebo for 8 weeks. The effec t of iron treatment was assessed by questionnaires and haematological and cognitive tests, which were done before treatment started and repe ated after the intervention. We used four tests of attention and memor y to measure cognitive functioning. intention-to-treat and per-protoco l analyses were done. Findings Of the 81 enrolled girls with non-anaem ic iron deficiency, 78 (96%) completed the study (39 in each group). F ive girls (three control, two treatment) developed anaemia during the intervention and were excluded from the analyses. Thus, 73 girls were included in the perprotocol analysis. Ethnic distribution, mean age, s erum ferritin concentrations, haemoglobin concentrations, and cognitiv e test scores of the groups did not differ significantly at baseline. Postintervention haematological measures of iron Status were significa ntly improved in the treatment group (serum ferritin 27 . 3 vs 12 . 1 mu g/L, p<0 . 001). Regression analysis showed that girls who received iron performed better on a test of verbal learning and memory than gi rls in the control group (p<0 . 02). Interpretation In this urban popu lation of non-anaemic iron-deficient adolescent girls, iron supplement ation improved verbal learning and memory.