Former LBW children who had been given additional iron during infancy showed significantly less aggressive and rule-breaking behaviour at age seven than the placebo group, reported the research team from Umeå University in Sweden.
The supplemented children also suffered fewer thought problems.
The results were part of an ongoing long-term Swedish study involving late preterm infants and marginally LBW full-term babies (2.0 – 2.5 kilograms (kg) at birth). Previous findings had already shown that iron supplementation between age 6-weeks and 6-months prevented iron deficiency anaemia (IDA) at the end of the intervention period. Additionally, the follow-up at age three and a half showed that supplemented children experienced fewer behavioural problems than those in the placebo group.
"Our findings suggest that iron supplementation may have long-lasting effects on behavioural functions in children born of a low birth weight," said first author Dr.Staffan Berglund. "This clinically important benefit from early iron supplementation gives further support to recommend iron supplementation of all low birth weight children, including those with marginally low birth weight."
The researchers found no difference in intelligence between the two groups. Additionally, iron status of the supplemented and non-supplemented children was similar at the age 7 follow-up.
The findings have major implications at the population level, since marginally LBW infants represent up to 5% of those born in wealthy countries and 15% in low-income nations.
The follow-up to the original double-blinded randomised controlled trial included 207 of the original 285 participants. The infants received either placebo, 1 or 2 milligrams/ kilogram/ day of iron in the form of ferrous succinate. The children’s parents completed two standardised questionnaires relating to behavioural and emotional problems. The researchers used the Wechsler Intelligence Scale for Children to assess the children's cognitive abilities.
Iron status: blood versus brain
The researchers noted, “In the present trial iron status at 6 months was not correlated with behavioural outcomes neither at 3.5 nor at 7 years. This may suggest that traditional measures of iron stores may not fully reflect availability of iron for the developing brain.”
Animal studies have indicated that the brain may start to be depleted of iron before IDA is detectable in the blood. Therefore, serum iron may not be a valid biomarker for brain iron status.
The scientists concluded, “Further research should focus on strategies to optimise cognitive performance and behaviour in children with marginally LBW, including assessment of optimal dose and duration of iron supplementation.”
Source: Pediatric Research
Accepted article preview online 27 September 2017 DOI: 10.1038/pr.2017.235
“Effects of iron supplementation of low birth weight infants on cognition and behavior at 7 years—a randomized controlled trial”
Authors: Staffan K Berglund, Anna Chmielewska et al