ArticlesEffects of stunting, diarrhoeal disease, and parasitic infection during infancy on cognition in late childhood: a follow-up study
Introduction
Cognitive function in children is affected by environmental and health-related factors.1, 2, 3 Risk factors that interfere with cognitive function are especially important during infancy because the first 2 years of life are an essential period of rapid growth and development. Chronic malnutrition during infancy, marked by stunting, has been related to poor cognitive function in late childhood in the Philippines,4 and in Jamaica,5 although the mechanisms are not fully understood.
Diarrhoea is both a cause and an effect of malnutrition, and can lead to linear growth retardation.6, 7, 8 Cryptosporidium parvum and Giardia lamblia, two common enteric infections often associated with diarrhoea, adversely affect growth and nutritional status, especially during infancy.9, 10, 11, 12, 13, 14 Research on the relation between cognitive function in children and diarrhoeal disease during infancy is limited. Guerrant and colleagues15 noted that diarrhoea during infancy was negatively correlated with three tests of cognitive function in Brazilian children. However, in this study, neither environmental nor health-related factors were considered, thus raising the possibility that the associations seen could be attributed to confounding.
The complex interrelations among malnutrition, diarrhoeal disease, and environmental factors such as socioeconomic status and education, make it difficult to determine the unique contribution of either malnutrition or diarrhoeal disease to cognitive development. For instance, because diarrhoeal disease can result in retarded growth,6, 10, 16 stunting becomes a potential confounder in the relation between diarrhoea and cognitive function.
We aimed to examine the associations between healthrelated factors during infancy and cognitive function in late childhood. First, we extended previous research that has linked stunting during infancy with poor cognitive function in late childhood by investigating multiple classifications of stunting and using a comprehensive, standardised, and widely accepted measure of cognitive function. Second, we assessed the independent effects of diarrhoeal disease, and C parvum and G lamblia infections during infancy on cognitive test scores in late childhood, after adjusting for stunting, schooling, and socioeconomic factors. If diarrhoeal disease during infancy is associated with cognitive function at 9-years-old after controlling for nutritional and environmental factors, our understanding of the long-term burden associated with diarrhoea and the health-related determinants of cognitive function will be greatly improved.
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Study setting
This study is a follow-up assessment of a cohort of children who were examined longitudinally from 1989–91. The study was done in Pampas de San Juan de Miraflores, a periurban shanty town in the outskirts of Lima, Peru. In 1989, most families in this community lived in houses constructed from woven thatch supported by wooden poles. Less than a half of families had latrines or sewage connections, and water was largely supplied by municipal trucks and stored in cisterns or barrels that often
Description of the sample
Table 1 shows the characteristics of the children. All children were enrolled in school from grade 2 to 5. 25 (18%) of 141 children had been held back in school once and required to repeat a grade; nine (6%) had been held back at least twice (table 2).
46 (32%) of 143 children were stunted at least once during infancy. Of these, ten (22%) were severely stunted. Most stunted children became stunted between 6 and 17 months of age. Nearly half of children who were stunted during infancy had
Discussion
We have shown that stunting during infancy has a strong adverse effect on cognitive function in late childhood. Severe stunting in the second year of life was associated with a 10-point reduction in intelligence quotient scores after adjustment for socioeconomic, schooling, and other significant factors. Previous studies have been limited by use of shorter, less comprehensive cognitive tests that are restricted to specific domains of intellectual ability and have relatively weak internal
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