Intellectual ability and nutritional status assessed through anthropometric measurements of Chilean school-age children from different socioeconomic status

This study was designed to investigate the interrelationships between intellectual ability (IA), nutritional status measured through anthropometric measurements and socio-economic and socio-cultural parameters. A representative sample of 4,509 school-age children according to grade, sex, type of school and geographic area was chosen from Chile's Metropolitan Region. School-age children 5 to 22 years of age belonged to elementary and high schools. The cross-sectional research was carried out in 1986-1987. IA was measured by means of the Raven's Progressive Matrices Test. The Z-scores for weight (Z-W) and height (Z-H) and the percentage of adequacy weight/height (% W/H), were compared with WHO tables; the Z-scores for head circumference (Z-HC) with Tanner tables and brachial anthropometric measurements with Frisancho standards. Socio-economic status (SES) was determined using Graffar's modified method. Statistical procedures included analysis of variance, Scheffe's test for comparison of means, correlation and regression. IA positively and significantly correlated with Z-HC, Z-H, Z-W and brachial anthropometric parameters; however, Z-HC is the anthropometric index with the greatest explanatory power in IA variance, followed by Z-H. Z-HC increased its explanatory power in IA variance with age and in school-age children 16 years of age or more this was the only anthropometric parameter that explained IA variance (F = 22.56, p < 0.0001; r(2) = 0.142). Independent of SES and age, in the total sample, Z-HC, sex, maternal and household head schooling, Z-H, sewerage and quality of housing, were the independent variables with the greatest explanatory power in IA variance (F = 43.03, p < 0.0001, r(2) = 0.176), in males, (F = 22.04, p < 0.0001, r(2) = 0.159) and in females (F = 25.98, p < 0.0001, r(2) = 0.191), the only group in which Z-H entered in the statistical model. Taking into consideration that HC is an indicator of nutritional background and brain development, these results may provide the basis for further research related with the impact of malnutrition at an earlier age on IA, HC and subsequent brain development and for improved nutritional and educational planning.