Interaction between vitamin A supplementation and chronic malnutrition on child development.

200 million pre-school age children are not developing properly. Delays in child development are associated with multiple factors. This study aims to analyze if vitamin A supplementation is associated with improved development and how this effect could be mediated by nutritional status. Population-based study surveyed a representative sample of 8000 households, 1232 children 0-35 months, in the state of Ceará, Brazil. The variables analysed included child developmental status, nutritional determinants and confounding factors. The main effects and interactions were evaluated using Cox regressive models. Vitamin A supplementation showed protective effect to delay in cognitive and motor development modified by interaction with nutritional status. While well-nourished supplemented children presented a 67% lower risk of cognitive delay (adjusted PRR = 0·33 [0·21-0·53]), stunted children had no benefit from supplementation (adjusted PRR = 0·97 [0·39-2·40]). Vitamin A supplementation has a protective effect on child development, but not in stunted children. This suggests that supplementation is effective in promoting child development, especially if associated to a joint effort to improve the nutritional status of children, given the importance of this mediator.