A Multilevel bayesian model for contextual effect of material deprivation

The relationship between socioeconomic factors and health has been studied in many circumstances. Whether the association takes place at individual level only, or also at population level (contextual effect) is still unclear.We present a multilevel hierarchical Bayesian model to investigate the joint contribution of individual and population-based socioeconomic factors to mortality, using data from the census cohort of the general population of the city of Florence, Italy (Tuscany Longitudinal Study, 1991–1995). Evidence supporting a contextual effect of deprivation on mortality at the very fine level of aggregation is found. Inappropriate modelling of individual and aggregate variables could strongly bias effect estimates.