Modeling water supply networks and gastrointestinal disorder symptoms with CAR models

TL;DR

This paper introduces a straightforward CAR model-based method to analyze water networks' impact on gastrointestinal symptoms, applied to Norwegian survey data, finding no significant link between water network connections and health conditions.

Contribution

The study proposes a simple, generic CAR model approach for directly modeling water networks in epidemiology, addressing a gap in current methods.

Findings

No significant association between water network connections and gastrointestinal symptoms.

The model converged after six hours of computation.

The approach effectively distinguishes spatial effects from water network influences.

Abstract

Background: The direct modeling of water networks is not a common practice in modern epidemiology. While space often serves as a proxy, it can be problematic. There are multiple ways to directly model water networks, but these methods are not straightforward and can be difficult to implement. This study suggests a simple approach for modeling water networks and diseases, and applies this method to a dataset of self-reported gastrointestinal conditions from a questionnaire-based population health survey in central Norway. Method: Our approach is based on a standard conditional autoregressive (CAR) model. An inverse matrix was constructed, with nodes weighted based on the distance to neighboring nodes within the networks. This matrix was then fitted as a generic model. To illustrate its possible use, we utilized data taken from a questionnaire-based population health survey, the HUNT Study, to measure self-reported gastrointestinal complaints. For hypothesis testing, we used the deviance information criterion (DIC) and included variables in a stepwise manner. Results: The full model converged after six hours. We found no relation between the water networks and the health conditions of people whose residences connected to different parts of the network in the geographical area studied. Conclusion: All water network models are simplifications of the real networks. Nevertheless, we suggest a valid approach for distinguishing between the general spatial effect and the water network using a generic model.