SEANUTS: Relationship between anthropometric indicators and cognitive performance in Southeast Asian school-aged children

Malnutrition together with poverty and sickness, affect the physical growth, behavior and learning abilities of children and adolescents.  More than 200 million children <5 years old are unable to reach their full potential for cognitive development due to poor nutrition.1 Unfortunately, adverse outcomes of early undernutrition on the intellectual abilities of children are irreversible and are carried over to adolescence.2 This has also been linked to impaired economic work productivity in adulthood. In the long run, the nutrition status may be linked to a nation’s economic growth and progress.

The South East Asian Nutrition Survey (SEANUTS) is a randomized multicenter cross-sectional study done in Indonesia, Malaysia, Thailand and Vietnam to assess the nutritional status of 16744 children with ages ranging from 6 months to about 12 years.3-7 One of the arms of SEANUTS was evaluating the relationship between anthropometric indicators and cognitive performance of 6746 school-aged children.3

Prior to the start of the survey, informed consent was obtained from the parents/legal guardian of the subjects. Subjects were grouped by age, sex and address (urban versus rural). Information on household composition, maternal education and income was collected using a structured questionnaire.3

Anthropometric indicators measured were height, weight and body mass index (BMI). Z-scores for height-for-age (HAZ), weight-for-age (WAZ) and BMI for age (BAZ) were computed using sex-specific World Health Organization (WHO) growth reference data. Classification of stunted, underweight and thin was made if children had HAZ, WAZ and BAZ <-2SD of the reference value. BAZ >+1SD and +2SD were set to classify children as overweight and obese, respectively. Children falling under BAZ >+3 were classified as severely obese.3-7

For the cognitive performance of children in Indonesia, Malaysia and Vietnam, intelligence quotient (non-verbal IQ) was measured using Raven’s Progressive Matrices (RPM). For Thai children, the Test of Non-Verbal Intelligence, third edition (TONI-3) was used. The subjects were classified into one of the five non-verbal IQ categories: ≥120 (superior); 110-119 (high average); 90-109 (average); 80-89 (below average) and 60-79 (low/borderline).3

Among the 6746 school-aged children in the four countries, 21% were underweight and 19% were stunted. Underweight and stunting was more prominent in Indonesia and Vietnam. Meanwhile, in Malaysia and Thailand, the prevalence of overweight (14% and 9.7%, respectively) and obesity (17.2% and 10.6%, respectively) was more common (Figure 1).3-7

Low/borderline IQ levels were noted in 15% of children. On the other hand, below average IQ levels were seen in 18.6% of children. Children in the rural areas had lower IQ levels compared to their urban-living counterparts, due in part to more learning opportunities in the urban setting.3

In these 4 studies, low WAZ, HAZ and BAZ significantly increased the odds of children having a low to below average IQ. The relationship between poor nutritional indicators and inferior cognitive function were comparable among the four countries in the SEANUTS study. A lower HAZ, indicative of long-term undernutrition, has been linked with poorer school performance and enrolment in school-aged children.8   Correlating overnutrition with IQ levels among Malaysian children, it was observed that overweight, obesity and severe obesity increased the odds of having lower non-verbal IQ. For the rest of the countries studied, the only parameter which increased the chances of having low and below average IQ was severe obesity. (Figure 2).3

Parents with impaired cognitive skills (either due to their own malnutrition history or lack of education) offer less intellectual stimulation in their children which may influence their learning. Intellectual stimulation influences not only cognitive abilities but physical growth as well.9 Similarly in the SEANUTS, it was observed that the higher the educational attainment of the mother, the higher the child’s IQ level was (r 0.26 and P<0.0001)3

Given the positive correlation between anthropometric indices and non-verbal IQ, nutrition in early life is important. It is, therefore, imperative for nutritional intervention to start earlier than during the school age period.10 However, with limited resources, targeted nutritional interventions for school-aged children may be employed. This is to ensure a positive linear growth potential and prevent further stunting in older children. Programs for improving maternal education, especially involving health and children’s welfare must also implemented. Improving the nutritional status of school-aged children contributes to educational achievement, which boosts an individual’s productivity and eventually the country’s long-term socio-economic development.10

References

  1. ICN2 Second International Conference on Nutrition. http://www.fao.org/about/meetings/icn2/toolkit/hunger-facts/en
  2. Black RE, Allen LH, Bhutta ZA et al. Lancet 2008; 369: 243-260.
  3. Sandjaja S, Poh BK, Rojoroonwasinkul N et al. British Journal of Nutrition 2013; 110: S57-S64.
  4. Sandjaja S, Budiman B, Harahap H et al. British Journal of Nutrition 2013; 110: S11-S20.
  5. Poh BK, Ng BK, Haslinda MDS et al. British Journal of Nutrition 2013; 110: S21-S35.
  6. Rojroonwasinkul N, Kijboonchoo K, Wimonpeerapattana W et al. British Journal of Nutrition 2013; 110: S36-S44.
  7. Nguyen BKL, Thi HL, Do VAN et al. British Journal of Nutrition 2013; 110: S45-S56.
  8. Grantham-McGregor SM, Walker SP. Nutrition, Health and Child Development: Advances in Research and Policy Implications, pp. 82-90.
  9. Webb KE, Horton NJ, Katz DL. European Journal of Clinical Nutrition 2005; 59: 618-620.
  10. Best C, Neufingerl N, van Geel et al. Food Nutr Bull 2010; 31: 400-417.