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|Title: ||Random-Effects Models in Investigating the Effect of Vitamin A in Childhood Diarrhea|
|Other Titles: ||Annals of Epidemiology|
|Authors: ||Andreozzi, Valeska Lima|
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|
|Appears in Collections:||Artigos Publicados em Periódicos (Nutrição)|
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