Iron status, anthropometric status and cognitive performance of black African school children aged 6–11 years in the Klerksdorp area
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AIM Poor iron status and under–nutrition among children are of concern not only in South Africa but worldwide. Both independent and combined associations between poor iron status, under–nutrition and cognitive development and function have been investigated. This mini–dissertation investigated possible associations between iron status indicators, anthropometric nutritional status and cognitive performance in the Beverage Fortified with Micronutrients (BeForMi) study population (black South African children aged 6–11 years in the North–West province of South Africa). METHODS The study was cross–sectional and based on the BeForMi study baseline data. Primary school children (n = 414) with the highest serum transferrin receptor (STR) and zinc protoporphyrin (ZnPP) levels were included. Anthropometric z–scores - BMI–for–age (BAZ), height–for–age (HAZ), and weight–for–age (WAZ) - and iron status indicators - haemoglobin (Hb), serum ferritin (SF), STR and ZnPP - were determined. The Kaufman Assessment Battery for Children, Second edition (KABC–II) was used to generate cognitive scores. RESULTS Fourteen percent of children were underweight (WAZ <= 2 SDs), 12.8% stunted (HAZ <= 2 SDs) and 8.4% wasted (BAZ <= 2 SDs). Of the children, 7.1% were anaemic (Hb < 11.5 g/dL), 13% iron depleted (Hb < 11.5 g/dL and SF < 12 ug/L) and 2.7% had iron deficiency anaemia (Hb < 11.5 g/dL and SF < 12 ug/L). Low iron stores (SF < 12 ug/L) were observed in 15.7% of the children. Positive correlations were found between SF and WAZ (r = 0.1, p = 0.047), Hb and HAZ (r = 0.13, p = 0.007) and WAZ (r = 0.13, p = 0.009). Positive correlations with small effect sizes were observed between some cognitive scores and z–scores (p < 0.05, r–value range 0.10 – 0.24). Negative correlations with small effect sizes were observed for the subtests Triangles and Rover (both subtests on simultaneous processing) with Hb (p = 0.008, r = –0.13) and SF (p = 0.04, r = –0.1) respectively. Higher HAZ, WAZ and education level of the head of household were all significantly associated with the likelihood that a child would fall within the upper quartile of Hb values in our study group (p = 0.036, p = 0.032 and p = 0.036 respectively). CONCLUSION The results suggested that under–nutrition was positively associated with poor iron status and lower cognitive scores in this study population. Further research, investigating specific effects of poor iron status at different stages of growth and the relationship with cognitive function later in life may help explain the negative correlations observed between current iron status indicators and cognitive scores.
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