Environmental and Ecological Statistics

, Volume 16, Issue 3, pp 341–353 | Cite as

Misspecification of within-area exposure distribution in ecological Poisson models

  • Léa Fortunato
  • Chantal Guihenneuc-Jouyaux
  • Margot Tirmarche
  • Dominique Laurier
  • Denis Hémon
Article

Abstract

Ecological studies enable investigation of geographic variations in exposure to environmental variables, across groups, in relation to health outcomes measured on a geographic scale. Such studies are subject to ecological biases, including pure specification bias which arises when a nonlinear individual exposure-risk model is assumed to apply at the area level. Introduction of the within-area variance of exposure should induce a marked reduction in this source of ecological bias. Assuming several measurements per area of exposure and no confounding risk factors, we study the model including the within-area exposure variability when Gaussian within-area exposure distribution is assumed. The robustness is assessed when the within-area exposure distribution is misspecified. Two underlying exposure distributions are studied: the Gamma distribution and an unimodal mixture of two Gaussian distributions. In case of strong ecological association, this model can reduce the bias and improve the precision of the individual parameter estimates when the within-area exposure means and variances are correlated. These different models are applied to analyze the ecological association between radon concentration and childhood acute leukemia in France.

Keywords

Ecological association Ecological bias Robustness Within-area exposure variability 

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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Léa Fortunato
    • 1
    • 2
  • Chantal Guihenneuc-Jouyaux
    • 1
    • 2
    • 3
  • Margot Tirmarche
    • 4
  • Dominique Laurier
    • 4
  • Denis Hémon
    • 1
    • 2
  1. 1.INSERM, U754Villejuif cedexFrance
  2. 2.Université Paris Sud, IFR69Villejuif cedexFrance
  3. 3.CNRS UMR 8145, UFR Biomédicale, Université Paris 5ParisFrance
  4. 4.IRSN/DRPH/SRBE/LEPIDFontenay-aux-RosesFrance

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