Three estimates of the association between linear growth failure and cognitive ability

• Published in: Tropical medicine & international health Vol. 14; no. 9; pp. 1020 - 1024
• Main Authors: Cheung, Y.B, Lam, K.F
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.09.2009; Blackwell Publishing Ltd; Blackwell
• Subjects: Altura; Biological and medical sciences; body height; Child; child development; Child Development - physiology; Children & youth; cognición; cognition; Cognition - physiology; Cognitive ability; Comparative studies; desarrollo del niño; développement de l’enfant; Epidemiologic Methods; Female; General aspects; Growth Disorders - epidemiology; Growth Disorders - psychology; growth retardation; Human growth; Humans; Male; Medical sciences; modelos estadísticos; modèles statistiques; Philippines; Psychometrics; retard de croissance; retraso en el crecimiento; Socioeconomic Factors; statistical models; stunting; taille corporelle; Philippines; Human; Growth; child development; Corporal biometry; Cognition; body height; stunting; Statistical model; Body size; statistical models; Tropical medicine; Child; Failure
• ISSN: 1360-2276; 1365-3156
• DOI: 10.1111/j.1365-3156.2009.02321.x

To compare three estimators of association between growth stunting as measured by height-for-age Z-score and cognitive ability in children, and to examine the extent statistical adjustment for covariates is useful for removing confounding due to socio-economic status. Three estimators, namely random-effects, within- and between-cluster estimators, for panel data were used to estimate the association in a survey of 1105 pairs of siblings who were assessed for anthropometry and cognition. Furthermore, a 'combined' model was formulated to simultaneously provide the within- and between-cluster estimates. Random-effects and between-cluster estimators showed strong association between linear growth and cognitive ability, even after adjustment for a range of socio-economic variables. In contrast, the within-cluster estimator showed a much more modest association: For every increase of one Z-score in linear growth, cognitive ability increased by about 0.08 standard deviation (P < 0.001). The combined model verified that the between-cluster estimate was significantly larger than the within-cluster estimate (P = 0.004). Residual confounding by socio-economic situations may explain a substantial proportion of the observed association between linear growth and cognition in studies that attempt to control the confounding by means of multivariable regression analysis. The within-cluster estimator provides more convincing and modest results about the strength of association.