Iron supplemented formula milk related to reduction in psychomotor decline in infants from inner city areas: randomised study

British Medical Journal, March 13, 1999 by J Williams, A Wolff, A Daly, A MacDonald, A Aukett, I W Booth

Abstract

Objective To compare the effect of unmodified cows' milk and iron supplemented formula milk on psychomotor development in infants from inner city areas when used as the main milk source.

Design Double blind, randomised intervention trial.

Setting Birmingham health centre.

Subjects 100 infants, mean age 7.8 months (range 5.7 to 8.6 months), whose mothers had already elected to use unmodified cows' milk as their infant's milk source.

Intervention Changing to an iron supplemented formula milk from enrolment to 18 months of age, or continuing with unmodified cows' milk.

Main outcome measures Developmental assessments using Griffiths scales at enrolment and at 18 and 24 months.

Results 85 participants completed the trial. There were no significant differences in haemoglobin concentration between the two groups at enrolment, but by 18 months of age 33% of the unmodified cows' milk group, but only 2% of the iron supplemented group, were anaemic (P [is less than] 0.001). The experimental groups had Griffiths general quotient scores that were not significantly different at enrolment, but the scores in both groups declined during the study. By 24 months the decrease in the mean scores in the unmodified cows' milk group was 14.7 whereas the decrease in the mean scores in the iron supplemented group was 9.3 (P [is less than] 0.02, 95% confidence interval 0.4 to 10.4). Mean subquotient scores were considerably lower in the unmodified cows' milk group at 24 months; significantly so for personal and social scores (P [is less than] 0.02, -5.4 to 17.2).

Conclusion Replacing unmodified cows' milk with an iron supplemented formula milk up to 18 months of age in infants from inner city areas prevents iron deficiency anaemia and reduces the decline in psychomotor development seen in such infants from the second half of the first year.

Introduction

Iron deficiency anaemia--that is, a haemoglobin concentration [is less than] 110.0 g/l--still occurs in 10 to 30% of preschool children living in inner cities in the United Kingdom.[1 2] There is a well established association between iron deficiency anaemia and developmental delay, and randomised studies providing oral iron supplements suggest that this may be causal.[3-8] We have previously shown that iron deficiency anaemia in infants and toddlers receiving unmodified cows' milk as their main milk source is eliminated by changing to an iron supplemented formula milk between 6 and 18 months of age.[9] Our study aimed to address an additional and pragmatic question: does randomisation to receive an iron supplemented formula milk between 6 and 18 months of age lead to an additional developmental advantage compared with continuing receipt of unmodified cows' milk? Detailed haematological and nutritional data from the study have already been published.[9] We now present the developmental outcomes.

Subjects and methods

Recruitment

Our keyworker (AD) received the names of all infants aged 6-8 months (567 identified) living in an inner city area of Birmingham from health visitors dealing with that area. AD visited the families, and the parents of only those infants whose mothers had already changed their infant's diet to unmodified cows' milk (n = 116) were asked to consider including their infant in the study. All mothers were given both verbal and written explanations of the study.

The mean age of infants at recruitment (47 boys and 53 girls) was 7.8 months (range 5.7 to 8.6 months). The population was 75% Caucasian, 24% AfroCaribbean, and 2% Asian (Indians). We excluded all preterm infants. Figure 1 shows the withdrawals and losses of participants from the study.

[Figure 1 ILLUSTRATION OMITTED]

The participants lived in a socially deprived area with poor housing, high unemployment, and poor public amenities--locally there was only one bank and no large supermarkets. The small local shops were expensive and had limited stocks of food, particularly fresh fruit and vegetables.

Power calculation-We performed a power calculation, which showed that if 47 participants were allocated to each dietary group this would provide a study power of 95% at a significance level of 5% for a difference in haemoglobin concentration of 7.5 g/l between groups.

Study design

After recruitment we randomised the infants in the pharmacy department at Birmingham Children's Hospital by random numbers in blocks of four to receive either an iron supplemented formula milk or to continue on unmodified cows' milk. We gave the results of randomisation to AD who was therefore unblinded. At 18 months, those infants randomised to change to an iron supplemented formula milk were transferred back to cows' milk, and both groups continued on the cows' milk until 24 months of age. Serial haematologicai, anthropometric, and developmental assessments using the Griffiths scales were made at enrolment and at 18 and 24 months of age.[10] We excluded those participants whose haemoglobin concentration decreased to [is less than] 90 g/l and referred them to their general practitioner.