PURPOSE: By adopting more appropriate and powerful statistical methods that fully exploit longitudinal structure, we re-analyze 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.
RCT Entities:
PURPOSE: By adopting more appropriate and powerful statistical methods that fully exploit longitudinal structure, we re-analyze 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.
Authors: Parminder S Suchdev; O Yaw Addo; Reynaldo Martorell; Frederick Ke Grant; Laird J Ruth; Minal K Patel; Patricia C Juliao; Rob Quick; Rafael Flores-Ayala Journal: Am J Clin Nutr Date: 2016-02-10 Impact factor: 7.045
Authors: Frederick K Grant; Rose Wanjala; Jan Low; Carol Levin; Donald C Cole; Haile S Okuku; Robert Ackatia-Armah; Amy W Girard Journal: Front Nutr Date: 2022-09-23
Authors: Carlos Antônio S T Santos; Rosemeire L Fiaccone; Nelson F Oliveira; Sérgio Cunha; Maurício L Barreto; Maria Beatriz B do Carmo; Ana-Lucia Moncayo; Laura C Rodrigues; Philip J Cooper; Leila D Amorim Journal: BMC Med Res Methodol Date: 2008-12-16 Impact factor: 4.615