Bayesian Detection of Clusters and Discontinuities in Disease Maps. (REVISED, February 1999)

An interesting epidemiological problem is the analysis of geographical variation in rates of disease incidence or mortality One goal of such an analysis is to detect clusters of elevated or lowered risk in order to identify unknown risk factors regarding the disease We propose a nonparametric Bayesian approach for the detection of such clusters based on Green s reversible jump MCMC methodology The prior model assumes that geographical regions can be combined in clusters with constant relative risk within a cluster The number of clusters the location of the clusters and the risk within each cluster is unknown This speci cation can be seen as a change point problem of variable dimension in irregular discrete space We illustrate our method through an analysis of oral cavity cancer mortality rates in Germany and compare the results with those obtained by the commonly used Bayesian disease mapping method of Besag York and