Lower systolic blood pressure at age 7 y in low-birth-weight children who received iron supplements in infancy: results from a randomized controlled trial

Background: Low birth weight (LBW) (<= 2500 g) is associated with iron deficiency in infancy and high blood pressure (BP) later in life. Objective: We investigated the effect of iron supplementation that was given to LBW infants on midchildhood BP. Design: The study was a randomized, double-blind, controlled trial that included 285 marginally LBW (2000-2500-g) infants at 2 Swedish centers between May 2004 and November 2007. The infants were randomly assigned to receive a placebo or 1 or 2 mg Fe . kg(-1) . d(-1) from 6 wk to 6 mo of age. In secondary analyses at the age of 7 y, systolic blood pressure (SBP), diastolic blood pressure (DBP), and the prevalence of children with BP within the hypertensive range (>90th percentile) were compared between the groups. Results: BP was analyzed via intention to treat in 189 children (66%). The mean +/- SD SBP was 103 +/- 8.1, 1016 7.5, and 101 +/- 7.8 mm Hg in children who had received the placebo (n = 70), 1 mg Fe . kg(-1) . d(-1) (n = 54), or 2 mg Fe . kg(-1) . d(-1) (n = 65), respectively. When the iron-supplemented groups were combined in covariate-adjusted analyses, the mean SBP in LBW children who had received iron supplementation in infancy was 2.2 mm Hg (95% CI: 0.3, 4.2 mm Hg) lower than in those who were unsupplemented (P = 0.026). Multivariate logistic regression showed that iron supplementation in infancy reduced the odds of having an SBP within the hypertensive range at 7 y of age (OR: 0.32; 95% CI: 0.11, 0.96). For DBP, there were no significant differences between the intervention groups. Conclusions: LBW children who receive iron supplementation (1 or 2 mg Fe . kg(-1) . d(-1)) in infancy have lower SBP at 7 y. This (to our knowledge) novel observation suggests that the increased risk of hypertension that is observed in children and adults who are born small might be reduced with early micronutrient interventions.