Spatial regression and spillover effects in cluster randomized trials with count outcomes

Karim Anaya-Izquierdo, Neal Alexander

Research output: Contribution to journalArticlepeer-review

2 Citations (SciVal)


This paper describes methodology for analyzing data from cluster randomized trials with count outcomes, taking indirect effects as well spatial effects into account. Indirect effects are modelled using a novel application of a measure of depth within the intervention arm. Both direct and indirect effects can be estimated accurately even when the proposed model is misspecified. We use spatial regression models with Gaussian random effects, where the individual outcomes have distributions overdispersed with respect to the Poisson, and the corresponding direct
and indirect effects have a marginal interpretation. To avoid spatial confounding, we use orthogonal regression, in which random effects represent spatial dependence using a homoscedastic and dimensionally-reduced modification
of the intrinsic conditional autoregression (ICAR) model. We illustrate the methodology using spatial data from a pair-matched cluster randomized trial against the dengue mosquito vector Aedes aegypti, done in Trujillo, Venezuela
Original languageEnglish
Pages (from-to)490-505
Issue number2
Early online date18 Jun 2020
Publication statusPublished - 1 Jun 2021


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