Supplementing Iron and Development in Breastfed Infants (SIDBI Study)

INTRODUCTION Iron is a nutrient of essential importance to the human organism. It takes part in energy production, oxygen transportation, and DNA synthesis and is indispensable for the development of the central nervous system. Iron is required for the myelination and production of neurotransmitters. It has been well documented that iron deficiency anemia (IDA) impairs child development. If the diagnosis of IDA is delayed, the deficits may be irreversible. Iron deficiency (ID) is the most common single nutrient deficiency and may affect 12% of children < 3 years of age in industrialized countries. ID has the potential to negatively influence psychomotor development. However, a causal relationship is not as clear as for IDA.

Previous studies have suggested that iron supplementation in healthy infants may enhance psychomotor development. A meta-analysis carried out by our group (Szajewska et al. ) aimed to evaluate the effects of iron supplementation in non-anemic pregnant women and in non-anemic healthy children aged <3 years on the mental performance and psychomotor development of children. The authors identified 7 randomized controlled trials (RCTs), 5 of which referred to supplementation during infancy. The polled results of 3 RCTs (n = 561) showed significant improvement on the Psychomotor Development Index (PDI) of the Bayley Scales of Infant Development at approximately 12 months of age in the iron-supplemented group compared with the control group (mean difference: 4.21; 95% CI 2.31 to 6.12). No significant effect of iron supplementation on the Mental Developmental Index (MDI) or behavior was found. Since the meta-analysis was performed, one relevant new study has been published. In this follow-up study, cognitive and school performance was measured at the age of 9 years. In the original study, infants were randomized to receive daily supplementation of iron, zinc, iron and zinc or placebo from 4 to 6 months of age and an assessment of iron and zinc status, as well as growth, was performed. No statistically significant difference in cognitive performance or school performance was reported between the four groups.

Given that ID is a common problem in small children, measures to prevent ID are being taken. According to Committee of Nutrition of the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN CoN), this should be achieved by the promotion of exclusive breastfeeding, the use of iron-fortified formulas when formula feeding is needed, the postponement of the introduction of whole cow milk as the main drink until the end of the first year of life, and the promotion of consumption of complementary foods rich in iron. More recently, the ESPGHAN CoN concluded that there is no convincing evidence that iron supplements should be provided to normal birth weight, exclusively breastfed infants during the first 6 months of life in populations with a low prevalence of IDA among 6-month-olds. In contrast, the American Academy of Pediatrics (AAP) recommends iron supplementation (1 mg/kg) in exclusively breastfed infants beginning at 4 months of age that should be continued until iron from complementary foods is available. Since in partially breastfed infants iron intake is uncertain, those who receive more than one half of their daily feedings as human milk, should also be supplemented with 1mg/kg iron beginning at 4 months.

Interventional studies of good methodological quality evaluating the role of iron supplementation of infants without anemia on their mental and psychomotor development are still needed.

MATERIALS AND METHODS

This is a randomized, double-blind, placebo-controlled trial.

• Participants Healthy singleton newborns born at term in a university hospital (St. Anna Mazowiecka Hospital, Department of Gynecology and Obstetrics, The Medical University of Warsaw, Poland) will be considered for inclusion. Their mothers will be approached shortly after birth and informed consent will be obtained. Parents will be contacted after approximately 3 months in order to establish weather an infant is being exclusively breastfed. If so, the infant will be randomised to receive either an iron supplement or a placebo from the age of 4 completed months until 9 months of age. Infants will also be recruited in well-baby clinics. Apart from recruitment, all study procedures will be pursued in The Department of Paediatrics, The Medical University of Warsaw, Poland.
• Sample size Sample size was calculated with the main outcome of fine and gross motor scales, cognitive and language development of the Bayley Scales of Infant and Toddler Development (Bayley III). In the previous editions of the test, these elements of the assessment were combined into Psychomotor Developmental Index (PDI) and Mental Developmental Index (MDI). To detect a difference of 5 points between the study groups with a power of 80% and α =0.05, a sample of 91 infants is needed in each study group. To account for 20% of loss to follow up, we aim to recruit 220 infants for the study.
• Interventions Infant in the experimental group will receive ferric pyrophosphate (7mg, 10mg or 15 mg depending on body weight daily, i.e. approx.1 mg/kg/day) or placebo from 4 months to 9 months of age.
• Allocation concealment and blinding A computer-generated randomisation list will be prepared. Blocks of ten will be applied. Randomisation will be stratified by infant's gender. Consecutive randomisation numbers (each number assigned to intervention or placebo in a blinded way) will be given to participants at enrollment. The study products will be delivered to the centre in boxes labelled with the letters A and B (meaning of A and B blinded, information deposited in a sealed envelope in a safe at the administrative part of the department). The boxes will also carry the information on the specific dose (7, 10 or 15mg). Subsequently, the letters A and B will be removed from the boxes by an independent person unrelated to the study planning and conduct, and replaced with numeric codes corresponding to the randomisation numbers, e.g. 001 - 7mg, 001 - 10mg, 001 - 15mg, 002 - 7mg, 002 - 10mg, 002 - 15mg etc. Sachets containing the study product will be packed in small packages of 30 pieces each. Neither the collective packages, nor the sachets will carry any labelling and all the unused sachets will always be returned by parents before switching to higher dose. The active product and placebo will be packed in identical sachets and the content will look and taste the same. Researchers, caregivers, outcome assessors, and a person responsible for the statistical analysis will be blinded to the intervention until a statistical report for the 12-months' developmental assessment is available. After that, both the caregivers and main outcome assessor will remain blinded until the completion of the study. The information on intervention assignment will be stored in a sealed envelope in a safe in the administrative part of the department.