Paediatrics

Iron deficiency is the most common nutrient deficiency globally,1 considered by the World Health Organisation (WHO) to be an important contributing factor to the global burden of disease.2 Iron deficiency is the primary cause of anaemia,3 which affects an estimated 47% of pre-school children (<5 years) and 25% of school-age children worldwide.2 

Iron is a fundamental nutrient, contributing to a broad host of biological processes. Lack of iron has been associated with negative physical and cognitive performance in adults, and impaired development in children.2 Children are at particular risk due to periods of rapid growth during infancy and adolescence.4 Although a clear causal link has yet to be established, studies suggest that iron deficiency may negatively impact on child behaviour, motor activity and cognitive development.5,9,10

The chart and table beneath show the prevalence of iron deficiency, iron deficiency anaemia and anaemia (with or without iron deficiency). A notable statistic is that the prevalence of iron deficiency in the United States is nine times greater among adolescent females, compared to adolescent males. This is primarily due to the onset of menstruation and the accompanying increase in blood loss.4

Prevalence of anaemia worldwide, 1993-20052 (% [95% CI])

Prevalence (%) of iron deficiency and iron deficiency anaemia, United States, 1988-19946
Sex and age (years) Iron Deficiency Iron Deficiency Anaemia
Both sexes
1-2 9 3
3-5 3 < 1
6-11 2 < 1
Non-pregnant females
12-15 9 2
16-19 11 3
Males
12-15 1 < 1
16-19 < 1 < 1

Iron in Infants and Children

Infants under 24 months of age (particularly 9-18 months) are at a high risk for iron deficiency due to both their rapid growth and the challenges associated with maintaining an adequate dietary iron intake in infants.6

Iron deficiency anaemia generally appears at approximately 9 months after birth.6 Healthy, term infants are born with sufficient iron stores to support their growth for the first 4-6 months  and it is only when these stores are depleted that the risk of iron deficiency anaemia increases.5

The majority of this stored iron is accreted during the last trimester of pregnancy, which leaves preterm infants at a greater risk of iron deficiency in the first six months than infants carried to term. 5 Preterm infants also tend to grow more rapidly, depleting their stores by 2-3 months of age.6 Other factors that increase an infant’s risk of low iron stores include maternal iron deficiency anaemia, diabetes or hypertension.5

Exclusive breast feeding for longer than 6 months also increases the risk of iron deficiency (at age 9 months) due to the low iron content of breast milk.5 Risks are also increased for those fed non-iron-fortified formula or cow’s milk.4  Cow’s milk is low in iron and cannot meet the iron needs of infants or toddlers regardless of the amount consumed.7

Early introduction (i.e., before age 1 year) of whole cow’s milk and consumption of >24 oz  (approximately 410mL, 680g) of whole cow’s milk daily after the 1st year of life are risk factors for iron deficiency because this milk has little iron, may replace foods with higher iron content, and may cause occult gastrointestinal bleeding 6. Cow milk is also known to inhibit the absorption of non-haem iron, as a result of the high concentration of calcium in cow’s milk7.

A combination of breast milk and iron-fortified formulas, or the introduction of iron-fortified cereals after 4 months of age, may help to reduce the risk of iron deficiency.6 As infants reach their third year the risk of iron deficiency decreases due to a slowing growth rate and an increasingly varied diet.6

Daily Iron Requirements Change with Age

Age Iron Requirement/Day
7 - 12 months 11 mg5
1 - 3 years old 7 mg5
4 - 8 years old 10 mg8
9 - 13 years old 8 mg8

As a result of these findings, it has been suggested that iron deficiency may play an important role in attention deficit hyperactivity disorder (ADHD).10 In one study, serum ferritin levels in 53 children with ADHD were found to be significantly lower than matched controls, while serum iron, haemoglobin and haematocrit levels were all within normal ranges.10 Serum ferritin levels also showed a significant negative correlation with symptoms as measured by the Connors’ Parent Rating Scale (CPRS).9 However, a larger study of 101 ADHD children found no correlation between serum ferritin and symptom severity.11 While this potential association still requires more rigorous analysis, evidence is emerging to suggest iron deficiency may at least play a role in certain subtypes of ADHD.11

Iron and Adolescents

The risk of iron deficiency rises again during adolescence as iron requirements increase in association with a new period of rapid growth and the onset of menstruation in female teenagers.4 Other factors that increase the risk of iron deficiency include vegetarianism and dieting. A study of school children in Britain found that 25% of vegetarians were anaemic, compared with 7% of meat eaters, while girls who had tried to lose weight in the past 12 months were 3 times more likely to be anaemic than those who had not.12

It might seem intuitive to think that overweight children are protected from iron deficiency anaemia due to their increased food intake. However the opposite appears to be true. Children and adolescents at risk of being overweight (defined as BMI at the 85th – 94th percentile), or overweight (≥95th percentile) were twice as likely to be iron deficient as those with normal weight.13 The majority of this increased prevalence was attributable to females, possibly due to the fact that overweight females tend to grow faster and mature earlier.13

Iron Requirements during Adolescence8

Gender Iron Requirement/Day
Male (14 - 18 yrs) 11 mg
Female (14 - 18 yrs) 15 mg

Table. Adapted from: McDermid and Lönnerdal, 2012.8

Testing for anaemia

Reflecting the change in iron needs for different age groups, the recommended haemoglobin thresholds for diagnosing iron deficiency anaemia also change by age and it is important to consider these when interpreting test results.

Definition of Anaemia Changes with Age6

Age (In years) Hemoglobin Concentration (< g/dL)
Children
1 to < 2 11.0
2 to < 5 11.1
5 to < 8 11.5
8 to < 12 11.9
Men
12 to < 15 12.5
15 to < 18 13.3
>= 18 13.5
Non-pregnant women and lactating women
12 to < 15 11.8
15 to < 18 12.0
>= 18 12.0