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A new approach for within-subject mediation analysis in AB/BA crossover designs

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Abstract
Crossover trials are widely used in psychological and medical research to assess the effect of reversible exposures. In such designs, each subject is randomly allocated to a sequence of conditions, enabling the evaluation of treatment differences within each individual. When there are but two possible exposures -each assessed during one of two time periods-, the crossover study is referred to as an AB/BA design. The goal of this presentation is to discuss mediation analysis in such simple crossover studies. We do so by considering within-subject mediation from a counterfactual-based perspective and by deriving expressions for the direct and indirect effects. Employing simulation studies, the performance of several existing methods will be assessed and compared to that of a novel one we propose. We show that the new method yields unbiased and efficient estimators for the direct and indirect effect, under a minimalistic set of `no unmeasured confounding'-assumptions. Finally, we illustrate the different techniques with data from a neurobehavioral study.
Keywords
Counterfacuals, AB/BA, Madiation analysis

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MLA
Josephy, Haeike, et al. “A New Approach for Within-Subject Mediation Analysis in AB/BA Crossover Designs.” Belgian Statistical Society, 21st Meeting, Abstracts, 2013.
APA
Josephy, H., Loeys, T., & Vansteelandt, S. (2013). A new approach for within-subject mediation analysis in AB/BA crossover designs. In Belgian Statistical Society, 21st Meeting, Abstracts. Ghent, Belgium.
Chicago author-date
Josephy, Haeike, Tom Loeys, and Stijn Vansteelandt. 2013. “A New Approach for Within-Subject Mediation Analysis in AB/BA Crossover Designs.” In Belgian Statistical Society, 21st Meeting, Abstracts.
Chicago author-date (all authors)
Josephy, Haeike, Tom Loeys, and Stijn Vansteelandt. 2013. “A New Approach for Within-Subject Mediation Analysis in AB/BA Crossover Designs.” In Belgian Statistical Society, 21st Meeting, Abstracts.
Vancouver
1.
Josephy H, Loeys T, Vansteelandt S. A new approach for within-subject mediation analysis in AB/BA crossover designs. In: Belgian Statistical Society, 21st Meeting, Abstracts. 2013.
IEEE
[1]
H. Josephy, T. Loeys, and S. Vansteelandt, “A new approach for within-subject mediation analysis in AB/BA crossover designs,” in Belgian Statistical Society, 21st Meeting, Abstracts, Ghent, Belgium, 2013.
@inproceedings{4443399,
  abstract     = {{Crossover trials are widely used in psychological and medical research to assess the effect of reversible exposures. In such designs, each subject is randomly allocated to a sequence of conditions, enabling the evaluation of treatment differences within each individual. When there are but two possible exposures -each assessed during one of two time periods-, the crossover study is referred to as an AB/BA design. The goal of this presentation is to discuss mediation analysis in such simple crossover studies. We do so by considering within-subject mediation from a counterfactual-based perspective and by deriving expressions for the direct and indirect effects. Employing simulation studies, the performance of several existing methods will be assessed and compared to that of a novel one we propose. We show that the new method yields unbiased and efficient estimators for the direct and indirect effect, under a minimalistic set of `no unmeasured confounding'-assumptions. Finally, we illustrate the different techniques with data from a neurobehavioral study.}},
  author       = {{Josephy, Haeike and Loeys, Tom and Vansteelandt, Stijn}},
  booktitle    = {{Belgian Statistical Society, 21st Meeting, Abstracts}},
  keywords     = {{Counterfacuals,AB/BA,Madiation analysis}},
  language     = {{eng}},
  location     = {{Ghent, Belgium}},
  title        = {{A new approach for within-subject mediation analysis in AB/BA crossover designs}},
  year         = {{2013}},
}