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Please use this identifier to cite or link to this item: http://repositorio.ufba.br/ri/handle/ri/12789

Title: Random-Effects Models in Investigating the Effect of Vitamin A in Childhood Diarrhea
Other Titles: Annals of Epidemiology
Authors: Andreozzi, Valeska Lima
Bailey, Trevor
Nobre, Flavio Fonseca
Struchiner, Claudio Jose
Barreto, Mauricio Lima
Assis, Ana Marlucia de Oliveira
Santos, Leonor Maria Pacheco
Keywords: Diarrhea;Vitamin A;Longitudinal Randomized Trial;Random Effects Models
Issue Date: 2006
Abstract: Purpose: By adopting more appropriate and powerful statistical methods that fully exploit longitudinal structure, we reanalyze and extend previously published results from a large community trial to investigate the effect of vitamin A supplementation on the prevalence and severity of diarrhea in young children. Methods: Generalized linear mixed models were used to allow for repeated measures in a reanalysis of a double-blind, randomized, placebo-controlled community trial conducted in a cohort of children in northeastern Brazil during 1 year. The response variable was weekly number of days with diarrhea for each child, and Markov Chain Monte Carlo methods were used to estimate model parameters. Results and conclusions: Random effects suitably accounted for the underlying heterogeneity between and within children, and our longitudinal analysis shows a significant beneficial effect of vitamin A supplementation that was inconclusive in previously reported simple summary analyses of these data. Risk for diarrhea infection was estimated to be 1.57 times greater for a child administered a placebo as opposed to vitamin A (95% credible interval, 1.17–2.12). Additionally, we identified previously unreported temporal effects in these data, showing a decreasing daily probability of diarrhea for both groups during the trial and treatment–time interaction.
Description: Texto completo: acesso restrito. p. 241–247
URI: http://www.repositorio.ufba.br/ri/handle/ri/12789
ISSN: 1047-2797
Appears in Collections:Artigos Publicados em Periódicos (Nutrição)

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