Researchers in Ireland looked at the associations between signs of microcytosis (small red blood cells due to low iron levels) and brain development in otherwise healthy children living in an affluent environment.

Having enough iron is very important for a child’s development. It is used to make hemoglobin in red blood cells, which carries oxygen around the body. Without enough iron a person can become anemic – that is, they have fewer healthy red blood cells. In iron-deficiency anemia, the blood cells are smaller than normal. This is called microcytosis. Iron is also important for the developing brain.

Iron levels can be evaluated using markers such as ferritin levels, which indicate the amount of iron stored in the blood, low red blood cells counts (anemia), or signs of microcytosis.  Several studies in young children have shown that iron deficiency—with or without anemia—is linked to signs of impaired brain development, such as poorer cognitive function (reasoning, memory, attention, language), with long-lasting effects into adulthood.

Infants and young children are at particular risk of iron deficiency. Although babies are born with iron stores that last for about six months, after this age they need to get iron from their diet. Whilst many products such as formula milk and cereals are fortified with iron, some children may not consume enough.

Most studies on iron deficiency have focused on the developing world or lower socio-economic groups, where iron-deficiency is a major health problem. Globally it is estimated that 25% of preschool children have iron-deficiency anemia. In contrast, most European countries have iron-deficiency anemia rates below 5%. Estimates vary widely, however, partly due to the lack of agreement on which blood tests to use and what should be the recommended levels of iron. Researchers in Ireland explored the associations between several blood tests – including ferritin levels and the size of red blood cells – and neurodevelopment in otherwise healthy two-year-old children from a low-risk affluent environment. They recently reported their findings in the British Journal of Nutrition.

The study was an analysis of a subgroup of children participating in a screening study of babies in Cork, Ireland performed between 2008 and 2011. Infants were followed from birth with assessments at day two and at two, six, 12, and 24 months. Detailed information on early health and diet was collected by interviewers and clinical assessments of their development performed by trained researchers. Blood tests were collected at 24 months to look at hemoglobin levels, red blood cell volume (for signs of microcytosis), ferritin levels (iron levels) and other markers of iron deficiency.

A total of 87 children were included in the analysis. Five children had an iron deficiency, but no child had iron-deficiency anemia according to current diagnostic guidelines. Thirteen children (15%) had microcytosis (small red blood cells) and these children had significantly lower scores on tests for cognitive development.

Using current diagnostic guidelines few children in this group had iron deficiency. However, microcytosis was seen in several children and associated with lower scores on cognitive development tests. The researchers concluded that this shows a need for larger studies to re-evaluate how we define and diagnose iron deficiency in young children. This would help us find the best combination of blood tests to identify any potential developmental problems related to suboptimal iron levels.

Written by Julie McShane, Medical Writer

Reference: McCarthy E, Kiely M, Hannon G, et al. Microcytosis is associated with low cognitive outcomes in healthy 2-year-olds in a high-resource setting. British Journal of Nutrition (2017), 118, 360-367. Doi:10.1017/S0007114517001945.

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